Component placing head and origin detection method of component placing head

ABSTRACT

A component placing head provided with spline shafts, which are each elevatably supported by two spline nuts, is provided with a cylindrical member that is fixed to the outer peripheral portions of the spline nuts and joins the spline nuts to each other to put the same into an integrated state. Further, the cylindrical member is rotatably supported on a head frame via two bearing sections, reducing the amount of the bearing sections to be provided. With this arrangement, high-accuracy component placement and downsizing of the component placing head can be achieved.

TECHNICAL FIELD

The present invention relates to a component placing head for holding aplurality of components by a plurality of component holding members andmounting the components on a circuit board and to an origin detectionmethod for the elevating operation of the component holding members.

BACKGROUND ART

In recent years, the electronic equipment market has earnestly demandedthe downsizing and the functional improvement of various electronicequipment with built-in component-mounted boards formed by placing andmounting a plurality of electronic components as components on a circuitboard. Therefore, it is required to carry out high-density mounting (orplacement) and high-accuracy mounting (or placement) of the electroniccomponents in forming the component-mounted board. It is furtherdemanded to reduce the production cost of component-mounted boards. Forexample, it is additionally demanded to improve the productivity perunit area of the component-mounted boards, i.e., the productivity perunit area in mounting the electronic components.

Such a component-mounted board is manufactured by placing the pluralityof electronic components on the circuit board and thereafter heating thecircuit board on which the electronic components are placed in a reflowmanner for the mounting of the electronic components placed on thecircuit board. Such a manufacturing process is called a componentmounting process (or component-mounted board producing process), whichis categorized roughly into a component placing process and a reflowprocess. The component placing process is carried out by an electroniccomponent placing apparatus provided with a component placing head thatsucks and holds a plurality of electronic components and places them ona circuit board.

FIG. 4 shows a sectional view of a head section 500 that is one exampleof the component placing head employed in such a conventional electroniccomponent placing apparatus (refer to, for example, Japanese unexaminedPatent Publication No. 2000-40900), and the structure of the headsection 500 will be described with reference to FIG. 4.

As shown in FIG. 4, the head section 500 is provided with a suctionnozzle 502 that is one example of the component holding member forreleasably holding an electronic component 501 such as a chip component,a shaft section 510 that is one example of the shaft section detachablyequipped with this suction nozzle 502, an elevation unit 520 for movingup and down the suction nozzle 502 equipped for the shaft section 510via this shaft section 510 and a rotating unit 530 for rotating thesuction nozzle 502 around its axis of rotation (its axial center ofrotation) via the shaft section 510.

Moreover, in order to improve the efficiency of the operation of placingthe electronic components 501 on a circuit board by providing the headsection 500 with a plurality of suction nozzles 502 capable ofindividually sucking and holding electronic components 501, the headsection 500 is provided with, for example, eight sets of shaftsections-510 and elevation units 520, and the shaft sections 510 and theelevation units 520 are supported by a head frame 540 of the headsection 500 so that the shaft sections 510 are arranged in a line (i.e.,the suction nozzles 502 are arranged in a line). Moreover, the rotatingunit 530 is able to rotate four suction nozzles 502 equipped formutually adjacent four shaft sections 510. In the head section 500capable of equipped with eight suction nozzles 502, two rotating units530 are provided while being supported by the head frame 540, by whichthe suction nozzles 502 equipped for the shaft sections 510 are maderotatable.

With regard to the head section 500 having the above-mentionedconstruction, the detailed structure of the shaft section 510 will bedescribed first. As shown in FIG. 4, each shaft section 510 is providedwith a spline shaft 511 that has a nozzle attaching portion 511 a, whichis one example of the holding member attaching portion capable ofdetachably equipped with the suction nozzle 502, at its end portion(lower end in the figure). Moreover, the spline shaft 511 is able torotate around its axis P of rotation by the rotating unit 530corresponding to this shaft section 510 and elevatable along the axis Pof rotation by the corresponding elevation unit 520. In the shaftsections 510, spline shafts 511 are elevatable and rotatable asdescribed above while being supported as the shaft sections 510 by thehead frame 540. This support structure will be described by using thepartially enlarged schematic view of the shaft section 510 shown in FIG.5.

As shown in FIG. 5, the shaft section 510 is further provided with afirst spline nut 512 (arranged on the upper side in the figure) and asecond spline nut 513 (arranged on the lower side in the figure), whichare arranged apart from each other along the axis P of rotation of thespline shaft 511, and which are two spline nuts that elevatably supportsthe spline shaft 511.

Moreover, as shown in FIG. 5, the first spline nut 512 and the secondspline nut 513 are supported via a bearing section 514 and a bearingsection 515, respectively, to a shaft frame 541 rotatably around theaxis P of rotation together with the spline shaft 511 on the innerperiphery of the shaft frame 541 that has a roughly cylindrical shape inthe head frame 540. Moreover, a roughly cylindrical outer cylindercollar 516 has its inner peripheral surface bonded to the outerperiphery of the first spline nut 512, and the outer periphery of theouter cylinder collar 516 is further rotatably supported on the innerperiphery of the shaft frame 541 via another bearing section 517,rotatably supporting the first spline nut 512. Moreover, an outercylinder collar 518 is similarly bonded to the second spline nut 513 androtatably supported via another bearing section 519.

With the shaft section 510 having the above-mentioned structure, thespline shaft 511 is elevatable along the axis P of rotation on the innerperiphery of the first spline nut 512 and the second spline nut 513 inthe shaft section 510, and both the first spline nut 512 and the secondspline nut 513 are made rotatable around the axis P of rotation on theinner periphery of the shaft frame 541.

The detailed structure of the rotating unit 530 will be described next.As shown in FIG. 4, the rotating unit 530 is provided with a shaft gear531 arranged so that the spline shaft 511 penetrates the cylindricalinner portion thereof. Moreover, the shaft gear 531 rotates the firstspline nut 512 by the rotation around the axis P of rotation thereof,allowing the spline shaft 511 to be rotated. Further, the rotating unit530 is provided with a cogged belt 532 engaged with the shaft gear 531,a driving gear 533 engaged with the cogged belt 532, and a rotatingdrive motor 534 to the end of its driving shaft 534 a of which thedriving gear 533 is fixed and which is able to rotate the driving shaft534 a in either the forward or reverse direction.

Moreover, as shown in FIG. 5, the shaft gear 531 has its lower endconnected to an upper end portion 516 a in the figure of the outercylinder collar 516 bonded to the first spline nut 512 via a ring-shapedcoupling 535. Moreover, the shaft gear 531 is supported on the innerperipheral surface of the shaft frame 541 so as to be rotatable aroundthe axis P of rotation via two bearing sections 536 at the upper end andthe lower end of its outer peripheral surface and so as not to come incontact with the spline shaft 511. Moreover, a plurality of teeth arecontinuously provided on the outer peripheral surface of the shaft gear531, the inner peripheral surface of the cogged belt 532 and the outerperipheral surface of the driving gear 533 in order to strengthen themutual engagement.

In this case, relations of planes among the shaft gear 531, the coggedbelt 532 and the driving gear 533 will be described here with referenceto the schematic explanatory view shown in FIG. 6. As shown in FIG. 6,one driving gear 533 and mutually adjacent four shaft gears 531 areengaged with one another inside one cogged belt 532. That is, byrotatively dividing the driving gear 533 in either the forward orreverse direction by the rotating drive motor 534, the cogged belt 532is driven to run in the rotational drive direction, allowing the fourshaft gears 531 to be concurrently rotated in the rotational drivedirection. Moreover, between the shaft gears 531 and between the shaftgear 531 located at the left-hand end in the figure and the driving gear533, four tension rollers 537 are provided so as to consistently urgethe cogged belt 532 toward the inside, consistently applying a constanttension to the cogged belt 532 and keeping a satisfactory engagementrelation among the gears.

With the rotating unit 530 having the above-mentioned structure, thespline shafts 511 corresponding to the four shaft gears 531 can berotated around the axis P of rotation concurrently in the samerotational direction via the coupling 535 and the first spline nut 512.

The elevation unit 520 will be described next. As shown in FIG. 4, theelevation unit 520 is provided with a ball screw shaft 521 supported byan elevation frame 542 of the head frame 540 rotatably around the axis Qof rotation (the axial center of rotation) thereof arranged roughlyparallel to the axis P of rotation of the spline shaft 511. Theelevation unit 520 is further provided with an elevation drive motor522, which is fixed to an upper end portion in the figure of the ballscrew shaft 521 and rotates the ball screw shaft 521 in either theforward or reverse direction around the axis Q of rotation, and anelevation nut section 523, which is meshed with the ball screw shaft 521and is moved up and down along the axis Q of rotation by the rotation ofthe ball screw shaft 521. Moreover, the elevation unit 520 is furtherprovided with a roughly L-figured elevation bar 524, which has one endfixed to the elevation nut section 523 and is moved up and down inaccordance with the ascent and descent of the elevation nut section 523,and the other end of the elevation bar 524 is arranged so as to beplaced between two bearing sections 525 attached to an upper portion ofthe spline shaft 511.

With the above-mentioned structure possessed by the elevation unit 520,when the elevation nut section 523 is moved up or down by the rotationof the ball screw shaft 521, the elevation bar 524 is moved up or downto push up or push down the spline shaft 511 via the bearing sections525 by its end portion, allowing the spline shaft 511 to be moved up anddown. It is to be noted that the ascent and descent of the elevation bar524 is guided by an LM guide 526 provided on the elevation frame 542.

Moreover, as a component placing head as described above, there hasconventionally been a head section provided with a plurality of suctionnozzles that serve as one example of the component holding memberarranged in a line. In the head section described above, the efficiencyof placing components on a circuit board has been improved by making thesuction nozzles concurrently suck and hold a plurality of components.Moreover, during the component placing operation by the head section,the elevating operation of the suction nozzles is to be performed.However, due to the necessity for performing individual elevatingoperation of the suction nozzles, the head section is provided withelevation units corresponding one to one to the suction nozzles.

Moreover, the head section described above is generally able toindividually perform the elevating operation of the suction nozzles bygenerally performing the elevating operation of the shaft sectionscapable of being detachably equipped with a suction nozzle at its end bythe respective elevation units (these shaft sections are also providedfor the head section while being arranged in a line). Moreover, theelevation units generally employ a mechanism employing a ball screwshaft section and a nut section meshed with it and rotatively drive theball screw shaft section by rotatively driving the drive motor attachedto the ball screw shaft section, thereby moving up and down the nutsection and enabling the elevating operation of the shaft section in thestate in which it can be moved up and down in synchronization with theascent and descent of the nut section while being engaged with the nutsection.

Next, FIG. 14 shows a schematic explanatory view of the elevation units410 of the head section 400 described above, and a method for detectingan origin that becomes a reference point of the ascent and descent ofeach of the elevation units 410 (refer to, for example, Japaneseunexamined Patent Publication No. 62-236655) will be described withreference to FIG. 14.

As shown in FIG. 14, the head section 400 is provided with eightelevation units 410, i.e., eight suction nozzles (not shown). Moreover,each of the elevation units 410 is provided with a ball screw shaftsection 411, a nut section 412, a drive motor 413 and an upper endposition restricting frame 414 for restricting the upper end position ofelevation of the nut section 412.

Moreover, the head section 400 is provided with a control section 409capable of individually controlling these elevation units 410. Each ofthe elevation units 410 is further provided with an encoder (not shown)capable of detecting the rotational angle of the drive motor 413 andoutputting this detection result to the control section 409.

When detecting the origin in the head section 400 described above, bydetecting the rotational angle by the encoder while rotatively drivingthe drive motor 413 in each of the elevation units 410 and assuming theposition of the nut section 412 on the elevating operation axis when theorigin of rotation in the rotational direction is detected as the origin(hereinafter referred to as a detection origin), each of the detectionorigins is set by the control section 409.

It is to be noted that these operations may be executed eitherindividually or concurrently in the elevation units 410. Subsequently,the elevating operation of each of the suction nozzles for the componentplacing operation is executed in the head section 400 regarding thedetection origin thus set as the origin on the actual elevatingoperation axis (hereinafter referred to as an axial origin).

DISCLOSURE OF INVENTION

However, in the head section 500 having the aforementioned structure,the first spline nut 512 and the second spline nut 513 have their outerperipheral surfaces rotatably supported via the bearing section 514 andthe bearing section 515, respectively, to the shaft frame 541 in each ofthe shaft sections 510. Accordingly, there is a problem that the outsidediameter dimensions of the bearing sections 514 and 515 are increased bythe first spline nut 512 and the second spline nut 513 interposed, andthe arrangement interval of the spline shafts 511 arranged in a linecannot be shortened, hindering the downsizing of the head section 500.

Moreover, when the outside diameter dimension of the spline shafts 511is reduced to solve the above-mentioned problem, it is sometimesdifficult to secure the rigidity required for the placement of theelectronic component 501. In such a case, it is sometimes the case wherethe spline shaft 511 is bent by an external force received during thereplacement of the suction nozzle 502 to be equipped or in another case,and this also leads to a problem that this arrangement cannot cope withthe placement of electronic components that require high-accuracypositioning.

Moreover, in each of the shaft sections 510, the first spline nut 512,the second spline nut 513, the bearing sections 541 and 515, the outercylinder collars 516 and 518 and the bearing sections 517 and 519 areindividually processed and thereafter assembled. Therefore, it isdifficult to make the axes of rotation coincide with the axis P ofrotation of the spline shaft 511. In such a case, there is also aproblem of displacement due to rotation occurring at the end of thesuction nozzle 502 equipped for the nozzle attaching portion 511 a ofthe spline shaft 511.

Moreover, it is also difficult to make the axes of rotation of themutually connected shaft gear 531, the coupling 535 and the outercylinder collar 516 coincide with the axis P of rotation for a similarreason, and joint portions of the members receive stress due to themisalignment of the axes of rotation. In such a case, there is also aproblem that the rotational accuracy is reduced and this arrangementcannot cope with the placement of electronic components that requirehigh-accuracy positioning.

Moreover, the rotating unit 530 has the structure in which one drivinggear 533 and the mutually adjacent four shaft gears 531 are inengagement inside one cogged belt 532. Therefore, even if a tension isconsistently applied to the tension rollers 537, particularly the areaof engagement of the cogged belt 532 with two shaft gears 531 out of thefour shaft gears 531 is less than that of the shaft gears 531 located atboth ends, possibly causing a slip between the two shaft gears 531 andthe cogged belt 532. In such a case, there is a problem that influenceis exerted on the rotational accuracy of the spline shafts 511, i.e.,the rotational accuracy of the suction nozzles 502, and this arrangementcannot cope with the placement of electronic components that requirehigh-accuracy positioning.

On the other hand, the aforementioned origin detection method in thehead section 400 does not confirm whether the detection origin actuallycoincides with the axial origin. Therefore, in the case where, forexample, an error occurs during the detection of the origin of rotationby the encoder, there is a problem that the detection origin does notcoincide with the axial origin, possibly causing a placement error inthe subsequent component mounting operation and failing in executingreliable placing operation. Moreover, there is also a problem thathigh-accuracy component placement can not be achieved if the situationdoes not get worse to such an extent that the placement error occurs.

As a method for solving such a problem, it can be considered to provideeach of the elevation units 410 individually with a sensor forconfirming the position of elevation of each of the nut sections 412 andconfirm that the detection origin coincides with the axial origin byeach of the sensors.

However, such an origin detection method passes for the case where thehead section is provided with one suction nozzle. However, when the headsection 400 is provided with eight suction nozzles and further wheneight elevation units 410 are provided so as to correspond one to one tothe suction nozzles, it is required to provide the elevation units 410with the respective sensors, i.e., provide the head section 400 witheight sensors in total. Accordingly, there is a problem that theconstruction of the head section 400 becomes complicated for the origindetection, and this becomes a factor of hindering the downsizing of thehead section, failing in suppressing the production cost of the headsection 400 low.

Accordingly, the object of the present invention is to solve theaforementioned problems and provide a component placing head and anorigin detection method by the component placing head capable of copingwith high-accuracy component placing operation on a circuit board by thecomponent placing head that holds a plurality of components by aplurality of component holding members and places the components on thecircuit board, permitting downsizing and improving the productivity perunit area in placing the components.

In order to achieve the aforementioned object, the present invention isconstructed as follows.

According to a first aspect of the present invention, there is provideda component placing head comprising:

a plurality of component holding members for releasably holding aplurality of components;

a plurality of shaft sections detachably equipped with each of thecomponent holding members;

elevation units for executing elevating operations of the componentholding members;

a rotating unit for executing rotational operation of each of thecomponent holding members for correction of holding postures ofcomponents held by the component holding members; and

a head frame that has shaft support sections for supporting the shaftsections and supports the elevation units and the rotating unit, thecomponent placing head being able to place the plurality of componentsheld by the component holding members on a circuit boards,

the shaft sections each comprising:

a spline shaft that has a holding member attaching portion fordetachably equipping with the component holding member at its endportion and is rotatable around an axis of rotation by the rotatingunit, elevatable along the axis of rotation by the elevation unit andarranged so as to penetrate the shaft support section;

a first spline nut and a second spline nut that are arranged apart fromeach other along the axis of rotation in vicinity of an upper end and alower end, respectively, of the shaft support section and elevatablysupport the spline shaft; and

cylindrical members that have inner peripheral portions fixed to outerperipheral portions of the first spline nut and the second spline nutand join the first spline nut to the second spline nut so as to put thespline nuts into an integrated state, and

the cylindrical members being supported in the vicinity of the upper endand the lower end of the shaft support section rotatably around the axisof rotation via two bearing sections, elevatably and rotatablysupporting the shaft section by the shaft support section.

According to a second aspect of the present invention, there is provideda component placing head as defined in the first aspect, wherein in eachof the shaft sections, the spline shaft and the cylindrical members areprocessed cutting so that the axis of rotation of the spline shaftcoincides with the axes of rotation of the cylindrical members in astate in which the first spline nut, the second spline nut and thecylindrical members are assembled with the spline shaft.

According to a third aspect of the present invention, there is provideda component placing head as defined in the first aspect, wherein thecylindrical members in each of the shaft sections are integrally formedof:

the first cylindrical member that has a nut fixation portion whose innerperipheral portion is fixed to the outer peripheral portion of the firstspline nut and a support portion whose outer peripheral portion issupported by one bearing section of the two bearing sections;

the second cylindrical member that has a nut fixation portion whoseinner peripheral portion is fixed to the outer peripheral portion of thesecond spline nut and a support portion whose outer peripheral portionis supported by the other bearing section of the two bearing sections;and

the cylindrical joint member that join the first cylindrical member tothe second cylindrical member, and

a stepped portion is formed between the support portion and the nutfixation portion so that a diameter of the outer peripheral portion ofthe support portion is smaller than a diameter of the inner peripheralportion of the nut fixation portion at each of the first cylindricalmember and the second cylindrical member.

According to a fourth aspect of the present invention, there is provideda component placing head as defined in the third aspect, wherein therotating unit comprises:

a transmission gear section whose inner peripheral portion is fixed tothe outer peripheral portion of the support portion of either one of thefirst cylindrical member and the second cylindrical member in each ofthe shaft sections;

a cogged belt that internally has a plurality of teeth capable of beingengaged with the transmission gear section and is engaged with thetransmission gear section; and

a rotating drive section that rotatively drives the cogged belt, whereby

the support portion is rotatively driven by rotatively driving thetransmission gear section around its axis of rotation via the coggedbelt by the rotating drive section in each of the shaft sections,enabling the spline shaft to be rotatably driven via the first splinenut and the second spline nut.

According to a fifth aspect of the present invention, there is provideda component placing head as defined in the fourth aspect, furthercomprising:

four shaft sections constructed of a first shaft section through afourth shaft section arranged mutually adjacent in a line as the shaftsections,

wherein the rotating unit comprising:

four transmission gear sections constructed of a first transmission gearsection through a fourth transmission gear section attached to the firstshaft section to the fourth shaft section, respectively, as thetransmission gear sections; and

a first cogged belt engaged with only the first transmission gearsection and the third transmission gear section among the fourtransmission gear sections and a second cogged belt engaged with onlythe second transmission gear section and the fourth transmission gearsection as the cogged belts, and

the rotating drive section comprising one rotating drive shaft sectionthat is engaged with the first cogged belt and the second cogged beltand is able to rotatively drive both the first cogged belt and thesecond cogged belt.

According to a sixth aspect of the present invention, there is provideda component placing head as defined in the third aspect or fourthaspect, wherein each of the elevation units comprises:

a ball screw shaft section supported rotatably around its axis ofrotation;

a rotating drive section that is fixed to an end portion of the ballscrew shaft section and for rotating the ball screw shaft section aroundthe axis of rotation;

an elevation nut section that is meshed with the ball screw shaftsection and is elevatable along the axis of rotation center of the ballscrew shaft section by the rotation of the ball screw shaft section; and

an engagement member that is fixed to the elevation nut section andengaged with the spline shaft of the corresponding shaft section and isable to move up and down the spline shaft in synchronization with theascent and descent of the elevation nut section, and

the elevation nut section is elevatable along the axis of rotation in astate in which the rotation of the ball screw shaft section around theaxis of rotation is restricted only by the engagement of the engagementmember with the spline shaft.

According to a seventh aspect of the present invention, there isprovided a component placing head as defined in the first aspect,

wherein the shaft sections are arranged mutually in a line,

the elevation units are comprised of a plurality of elevation units thatcorrespond one to one to the shaft sections and for moving up and downthe shaft sections along the respective axes of rotation,

each of the elevation units comprises:

a ball screw shaft section supported rotatably around its axis ofrotation;

a rotating drive section that is fixed to an end portion of the ballscrew shaft section and for rotating the ball screw shaft section aroundthe axis of rotation;

an elevation nut section that is meshed with the ball screw shaftsection and is elevatable along the axis of rotation of the ball screwshaft section by the rotation of the ball screw shaft section; and

an engagement member that is fixed to the elevation nut section andengaged with the corresponding shaft section and able to move up anddown the shaft section in synchronization with the ascent and descent ofthe elevation nut section,

the component placing head further comprising:

a light transmission unit that is provided with a light-projectingsection and a light-receiving section arranged so as to be opposite toeach other in a direction along an array direction of the ball screwshaft sections and able to arrange the elevation nut sections betweenthe light-projecting section and the light-receiving section and able todetect presence or absence of interruption of light by the elevation nutsection by receiving the light emitted from the light-projecting sectiontoward the light-receiving section by the light-receiving section;

a plurality of rotational angle detecting sections capable of detectinga rotational angle of the rotating drive section provided for each ofthe elevation units; and

an origin detection control section is operable to set an origin ofelevation of the elevation nut section by detecting the rotational angleby the rotational angle detecting section in each of the elevationunits, individually move down the elevation nut sections located inrespective set origin positions so that the light emitted from thelight-projecting section is received by the light-receiving sectionwithout being interrupted, detect the interruption of light emitted fromthe light-projecting section by the lowered elevation nut section by thelight-receiving section in a position where the elevation nut section islowered from each of the set origins by a prescribed light interruptiondimension, thereby confirming the fact that the set origins are originsof elevation to execute the detection of the origins.

According to a eighth aspect of the present invention, there is provideda component placing head as defined in the seventh aspect, wherein eachof the elevation units further comprising:

an overload detecting section capable of detecting overload of therotating drive section; and

restricting portions that are fixed to the ball screw shaft sectionwhile being located apart from each other and for restrictingmechanically the upper end position and the lower end position ofelevation of the elevation nut section, and

the origin detection control section is operable to reverse therotational direction of the rotating drive section when the overload ofeach of the rotating drive sections is detected by the respectiveoverload detection section by moving each of the elevation nut sectionsto the upper end position of the elevating operation and bringing eachof the elevation nut sections in contact with the restricting portion inthe upper end position, and detect the rotational angle by therotational angle detection section in each of the elevation units afterthe reversing, whereby set the position along the axial center of theelevation nut section when the origin of rotation of the rotating drivesection is detected at a first time as the origin of elevation.

According to a ninth aspect of the present invention, there is provideda component placing head as defined in the seventh aspect, wherein thelight-projecting section and the light-receiving section are arranged sothat the light emitted from the light-projecting section can betransmitted and received by the light-receiving section in each ofpositions located apart by the prescribed light interruption dimensiondownwardly along the axis of rotation of each of the ball screw shaftsections from each of the origins.

According to a tenth aspect of the present invention, there is provideda component placing head as defined in any one of the seventh aspectthrough ninth aspect, wherein each of the elevation nut sections canconsistently interrupt the light emitted from the light-projectingsection in the position of elevation of the elevation nut sectionbetween each of positions located apart by the prescribed lightinterruption dimension downwardly along each of the axes of rotationfrom each of the origins and a lower end position of elevation of theelevation nut section.

According to a eleventh aspect of the present invention, there isprovided an origin detection method for a component placing head having:

a plurality of shaft sections that has an end portion provided with aplurality of component holding members for releasably holding componentsand are arranged in a line;

a plurality of elevation units that correspond one to one to the shaftsections and for moving up and down each of the shaft sections along itsaxis of rotation, the elevation units being comprised of,

a ball screw shaft section supported rotatably around its axis ofrotation,

a rotating drive section that is fixed to an end portion of the ballscrew shaft section and for rotating the ball screw shaft section aroundthe axis of rotation,

an elevation nut section that is meshed with the ball screw shaftsection and is elevatable along the axis of rotation of the ball screwshaft section by the rotation of the ball screw shaft section, and

an engagement member that is fixed to the elevation nut section andengaged with the corresponding shaft section and able to move up anddown the shaft section in synchronization with the ascent and descent ofthe elevation nut section; and

a light-projecting section and a light-receiving section, which arearranged opposite to each other in a direction along an array directionof the ball screw shaft sections and are able to arrange each of theelevation nut sections between the light-projecting section and thelight-receiving section and are able to detect the presence or absenceof the interruption of light by the elevation nut section by receivingthe light emitted from the light-projecting section toward thelight-receiving section by the light-receiving section, whereby thecomponents held by the component holding members are placed on thecircuit board,

the method comprising:

setting an origin of elevation of the elevation nut section by detectingthe rotational angle of the rotating drive section in each of theelevation units;

individually moving down the elevation nut sections located in therespective set origin positions so that the light emitted from thelight-projecting section is received by the light-receiving sectionwithout being interrupted; and

confirming the fact that each of the set origins are origins ofelevation by detecting the interruption of light emitted from thelight-projecting section by the lowered elevation nut section by thelight-receiving section in a position where the elevation nut section islowered from each of the set origins by a prescribed light interruptiondimension to execute the detection of the origins.

According to a twelfth aspect of the present invention, there isprovided an origin detection method for the component placing headdefined in the eleventh aspect, wherein,

moving each of the elevation nut sections to an upper end position ofits elevating operation,

reversing the rotational direction of the rotating drive section whenoverload of each of the rotating drive sections is detected at each ofthe upper end positions, and

detecting the rotational angle of each of the elevation units after thereversing, the position along the axis of rotation of the elevation nutsection when the origin of rotation of the rotating drive section isdetected at a first time can be set as the origin of elevation.

According to a thirteenth aspect of the present invention, there isprovided an origin detection method for the component placing headdefined in the eleventh aspect, wherein the light-projecting section andthe light-receiving section are arranged so that the light emitted fromthe light-projecting section can be transmitted and received by thelight-receiving section in each of positions located apart by theprescribed light interruption dimension downwardly along the axis ofrotation of each of the ball screw shaft sections from each of theorigins.

According to a fourteenth aspect of the present invention, there isprovided an origin detection method for the component placing headdefined in any one of the eleventh aspect through thirteenth aspect,

wherein each of the elevation nut sections can consistently interruptthe light emitted from the light-projecting section in the position ofelevation of the elevation nut section between each of positions locatedapart by the prescribed light interruption dimension downwardly alongthe axis of rotation from each of the origins and a lower end positionof elevation of the elevation nut section, and

movement of each of the component holding members in a direction along asurface of the circuit board is inhibited in the state in which light isinterrupted.

According to the first aspect of the present invention, the cylindricalmember is fixed to the outer peripheral portions of the first spline nutand the second spline nut, which are arranged apart from each other inthe vicinity of the upper end and the lower end of the shaft supportsection at the shaft sections of the component placing head andelevatably support the spline shaft along the axis of rotation thereof.With this arrangement, the two spline nuts of the first spline nut andthe second spline nut can be joined to each other and put into anintegrated state.

Furthermore, the cylindrical member is supported in the vicinity of theupper end and the lower end of the shaft support section rotatablyaround the axis of rotation via the two bearing sections. With thisarrangement, the two spline nuts put in the above-mentioned integratedstate can be supported rotatably around the axis of rotation via the twobearing sections to the shaft support section. That is, the two splinenuts can be rotatably supported by the two bearing sections, and theamount of the bearing sections to be provided for supporting the splinenuts can be reduced in the bearing sections.

Therefore, the bearing sections can easily be assembled in the componentplacing head, and the production cost of the component placing head canbe reduced. In addition, since the amount of the bearing sections to beprovided can be reduced, the rotational center positional alignment ofthe axis of rotation of each of the spline shafts with the axis ofrotation of each of the bearing sections (i.e., also the axis ofrotation of the cylindrical member) can be facilitated. The amount ofdisplacement of the axis of rotation due to the rotation of thecomponent holding member equipped for each of the shaft sections can bereduced, and the rotational accuracy can be improved. Accordingly, therecan be provided a component placing head capable of coping with thecomponent placement that requires high-accuracy component positioning.

According to the second aspect of the present invention, the splineshaft and the cylindrical member are machined so that the axis ofrotation of the spline shaft coincides with the axis of rotation of the-cylindrical member in the state in which the spline shaft, the firstspline nut, the second spline nut and the cylindrical member areassembled into an integrated body before each of the shaft sections areassembled and attached to the component placing head. With thisarrangement, the above-mentioned axes of rotation can be made to roughlycoincide with one another with high accuracy. Therefore, the componentplacing head, which is assembled by inserting the shaft sections intothe shaft frame while being rotatably supported, can cope with thecomponent placement that require high-accuracy component positioning.

According to the third aspect of the present invention, in each of theshaft sections, the cylindrical member is integrally formed of: thefirst cylindrical member provided with the nut fixation portion whoseinner peripheral portion is fixed to the outer peripheral portion of thefirst spline nut arranged in the vicinity of either one of the upper endand the lower end of the shaft support section and the support portionsupported by one bearing section out of the two bearing sections by itsouter peripheral portion; the second cylindrical member provided withthe nut fixation portion whose inner peripheral portion is fixed to theouter peripheral portion of the second spline nut arranged in thevicinity of the other one and the support portion is supported by theother bearing section out of the two bearing sections by its outerperipheral portion; and the cylindrical joint member for joining thefirst cylindrical member to the second cylindrical member, and thestepped portion is formed between the support portion and the nutfixation portion so that the diameter of the outer peripheral portion ofthe support portion is smaller than the diameter of the inner peripheralportion of the nut fixation portion in each of the first cylindricalmember and the second cylindrical member. With this arrangement, thediameter of the inner peripheral portion of each of the bearing sectionscan be made smaller than the diameter of the outer peripheral portion ofeach of the spline nuts.

As described above, when the diameter of the inner peripheral portion ofthe bearing section can be reduced, the outside diameter of each of theshaft sections can be reduced, and the arrangement interval between thespline shafts provided for the component placing head can be narrowed,allowing a downsized component placing head to be provided. In such acase, the component placing apparatus provided with the downsizedcomponent placing head can also be downsized, and there can be provideda component placing head capable of improving the productivity per unitarea in placing components by reducing the installation area of thecomponent placing apparatus.

Conversely, when the outside diameter of each of the shaft sections isnot reduced, the outside diameter of the spline shaft can be increasedwithout changing the outside diameter of the shaft section, and therigidity of the spline shaft can be improved. In such a case, forexample, even when an external force is applied to the spline shaftduring the replacement of the component holding member or the like, theoccurrence of displacement of the axis of rotation of the spline shaftcan be prevented by the rigidity, and a component placing head that hashigher rotational accuracy can be provided.

According to the fourth aspect of the present invention, in the rotatingunit of the component placing head, dissimilarly to the conventionalcase where the transmission gear section is attached to the shaftsection via the coupling, the transmission gear section is attached tothe shaft section in the state in which the inner peripheral portionthereof is directly fixed to the outer peripheral portion of the supportportion of either one of the first cylindrical member and the secondcylindrical member. With this arrangement, the misalignment of the axisof rotation of the transmission gear section with respect to the axis ofrotation of the spline shaft due to the existence of the coupling can bereduced. Therefore, the concentricity of the axes of rotation of thetransmission gear section and the spline shaft can be improved, andthere can be provided a component placing head of which the rotationalaccuracy is improved.

According to the fifth aspect of the present invention, in the rotatingunit, dissimilarly to the conventional case where the four transmissiongear sections are engaged with one another by one cogged belt, therotating unit is provided with the two cogged belts of the first coggedbelt and the second cogged belt. The first cogged belt is engaged withthe first transmission gear section and the third transmission gearsection, while the second cogged belt is engaged with the secondtransmission gear section and the fourth transmission gear section. Withthis arrangement, the areas of engagement of the four transmission gearsections can be uniformed in the state in which the areas of engagementof the cogged belts with respect to the respective transmission gearsections is sufficiently secured. With this arrangement, the deviationin the rotational accuracy, which has occurred due to the deviation inthe area of engagement, can be canceled. In addition, by sufficientlysecuring the area of engagement, there can be provided a componentplacing head capable of reliably rotating each of the transmission gearsections and rotating each of the component holding members with highaccuracy.

According to the sixth aspect of the present invention, theconstruction, in which the elevation nut section can be moved up anddown along the axial center by the fact that the rotation of the ballscrew shaft section around the axis of rotation is restricted only bythe engagement between the engagement member and the spline shaft ineach of the elevation units of the component placing head, can beachieved by improving the rigidity (i.e., strength) with the outsidediameter of the spline shaft formed large by the support structure withthe outside diameter of the bearing section maintained.

Therefore, the restricting member (e.g., LM (Line Motion) guide), whichhas been needed for receiving the rotation moment transmitted from theelevation nut section to the spline shaft via the engagement member in asupport structure such that the outside diameter of the spline shaftcannot be formed large as in the conventional component placing head,can be made unnecessary in the component placing head of theaforementioned sixth aspect. With this arrangement, there can beprovided a further downsized component placing head capable of reducingthe dimension between the axis of rotation of the spline shaft and theaxis of rotation of the ball screw shaft section by the needlessness ofthe conventional restricting member and improving the productivity perunit area.

According to the seventh aspect or the eleventh aspect of the presentinvention, instead of detecting the rotational angle of each of therotating drive sections using each of the rotational angle detectingsections provided for the component placing head, setting the origin ofelevation of each of the elevation nut sections and thereafter executingthe component placing operation by moving up and down each of thecomponent holding members in the component placing head directly usingthe set origins without confirming the set origins, it is confirmedwhether or not these set origins actually coincide with the origins ofelevation. Therefore, even if a malfunction (setting error) occursduring the setting of each of the origins, the setting error can surelybe detected, and the placement error due to the fact that the set origindoes not coincide with the origin of elevation can be prevented fromoccurring in advance during the subsequent component placing operationby the component placing head, and reliable origin detection can beperformed.

Moreover, the above-mentioned origin detection can be achieved byproviding the component placing head with only one light transmissionunit, which is provided with the light-projecting section and thelight-receiving section arranged so as to be opposite to each other inthe direction along the array direction of the ball screw shaft sectionsand is able to arrange each of the elevation nut sections between thelight-projecting section and the light-receiving section and able todetect the presence or absence of the interruption of the light by theelevation nut section by receiving the light emitted from thelight-projecting section toward the light-receiving section by thelight-receiving section.

That is, by individually moving down each of the elevation nut sectionslocated in the respective set origin positions so that the light emittedfrom the light-projecting section of the provided one light transmissionunit is received by the light-receiving section without beinginterrupted and detecting the interruption of the light emitted from thelight-projecting section by the lowered elevation nut section by thelight-receiving section in the position lowered by the prescribed lightinterruption dimension from each of the set origins, it can be confirmedthat each of the set origins is the origin of the elevation, and thedetection of each of the origins can be performed.

Therefore, even if a plurality of component holding members are providedas in the case of the aforementioned component placing head, the origincan be confirmed by the provision of one light transmission unit as thecomponent placing head without providing each of the elevation unitswith a unit for confirming the origin. Accordingly, there can beprovided a component placing head capable of executing reliable origindetection with a simpler construction, and the production cost can alsobe suppressed low. As a result, there can be provided a componentplacing head capable of achieving the downsizing of the componentplacing head while being able to cope with the high-accuracy componentplacing operation and improving the productivity per unit area duringthe component placing.

Moreover, the light transmission unit is able to detect whether or notthe light emitted from the light-projecting section is directlyinterrupted by the elevation nut section, so that the construction ofthe component placing head can be simplified providing no special lightshield plate (e.g., DOG etc.) for the interruption of the light.

According to the eighth aspect or the twelfth aspect of the presentinvention, in the component placing head, each of the elevation units isfurther provided with the overload detecting section capable ofdetecting the overload of the rotating drive section and each of therestricting portions that are fixed to the ball screw shaft sectionwhile being located apart from each other and mechanically restricts theupper end position and the lower end position of elevation of theelevation nut section. By reversing the rotational direction of therotating drive section when the overload of each of the rotating drivesections is detected in each of the overload detection sections bymoving each of the elevation nut sections to the upper end position ofthe elevating operation and bringing each of the elevation nut sectionsin contact with the restricting portion in the upper end position in theorigin detection control section and detecting the rotational angle bythe rotational angle detection section in each of the elevation unitsafter the reversing, the position of the elevation nut section along theaxial center when the origin of rotation of the rotating drive sectionis detected at the first time can be set as the origin of the elevation.With this arrangement, each of the origins can be set by using each ofthe rotational angle detection sections and each of the overloaddetection sections. Therefore, in addition to the effects of the seventhaspect or the eleventh aspect, each of the origins can be detected withthe simple construction of each of the rotational angle detectionsections and each of the overload detection sections providing thecomponent placing head with neither complicated mechanism nor unit forthe detection of each of the origins.

According to the ninth aspect or the thirteenth aspect of the presentinvention, the light-projecting section and the light-receiving sectionare arranged so that the light emitted from the light-projecting sectioncan be transmitted and received by the light-receiving section in eachof the positions located apart by the prescribed light interruptiondimension downwardly along the axial center of each of the ball screwshaft sections from each of the origins. With this arrangement, byconfirming the interruption of the light emitted from thelight-projecting section by the lowered elevation nut section in theposition in which the elevation nut section is lowered from the setorigin by the prescribed light interruption dimension, it can beconfirmed that the set origin is the origin of the elevation, and thedetection of the origin can be executed reliably and correctly.

According to the tenth aspect or the fourteenth aspect of the presentinvention, each of the elevation nut sections can consistently interruptthe light emitted from the light-projecting section in the position ofelevation of the elevation nut section between each of the positionslocated apart by the prescribed light interruption dimension downwardlyalong the axial center from each of the origins and the lower endposition of elevation of the elevation nut section. With thisarrangement, when the interruption of light is detected by the lighttransmission unit, by inhibiting the movement of the main body of thecomponent placing head along the surface of the circuit board, there canbe prevented the interference of the component holding members with theconstituent members of the electronic component placing apparatusprovided with the above-mentioned component placing head and the othercomponents placed on the circuit board. That is, in the componentplacing head, the detection of light by the light transmission unit canbe used as interference prevention interlock of each of the componentholding members in addition to the use thereof for the origin detection.This obviates the need for providing the component placing head with aspecial sensor or the like for providing the above-mentioned interlockand allows the construction of the component placing head to be madesimpler.

BRIEF DESCRIPTION OF DRAWINGS

These and other aspects and features of the present invention willbecome clear from the following description taken in conjunction withthe preferred embodiments thereof with reference to the accompanyingdrawings, in which:

FIG. 1 is a sectional view of a head section according to a firstembodiment of the present invention;

FIG. 2 is a partially enlarged schematic sectional view of a shaftsection in the head section of FIG. 1;

FIG. 3 is a schematic explanatory view showing the relation ofengagement among driving gears, shaft gears and cogged belts in arotating unit of the head section of FIG. 1;

FIG. 4 is a sectional view of a conventional head section;

FIG. 5 is a partially enlarged schematic sectional view of a shaftsection in the conventional head section;

FIG. 6 is a schematic explanatory view showing the relation ofengagement among a driving gear, shaft gears and a cogged belt in arotating unit of the conventional head section;

FIG. 7 is a sectional view of part of a head section according to amodification example of the first embodiment;

FIG. 8 is a schematic sectional view of a head section according to asecond embodiment of the present invention;

FIGS. 9A, 9B, 9C, and 9D are schematic explanatory views showing theorigin detecting operation of each of elevation nut sections in the headsection of FIG. 8, where FIG. 9A shows an initial state at the start ofthe origin detecting operation, FIG. 9B shows a state in which oneelevation nut section is moved up to the upper end position of theelevation thereof, FIG. 9C shows a state in which the detection originis set in each of the elevation nut sections, and FIG. 9D shows a statein which one elevation nut section is moved down to the optical axisposition of a light transmission unit to confirm whether or not thedetection origin coincides with the axial origin;

FIGS. 10A, 10B, and 10C are schematic explanatory views (also views inthe direction of arrow A of the head section of FIGS. 9A through 9D)showing the position of elevation of the elevation nut section duringthe origin detecting operation in each of the head sections of FIG. 8,where FIG. 10A shows a state in which the elevation nut section islocated at the detection origin, FIG. 10B shows a state in which theinterruption of light is detected by the light transmission unit, andFIG. 10C shows a state in which the elevation nut section is furtherlowered from the state of FIG. 10B;

FIG. 11 is a schematic explanatory view showing the height position ofelevation of each of the elevation nut sections in the head section ofFIG. 8;

FIG. 12 is a flowchart showing the procedure of the origin detectingoperation in the head section of FIG. 8;

FIG. 13 is a flowchart showing the procedure of the origin detectingoperation in the head section of FIG. 8; and

FIG. 14 is a schematic explanatory view showing the origin detectingoperation in a conventional head section.

BEST MODE FOR CARRYING OUT THE INVENTION

Before the description of the present invention proceeds, it is to benoted that like parts are designated by like reference numeralsthroughout the accompanying drawings.

Embodiments of the present invention will be described in detail belowwith reference to the drawings.

FIRST EMBODIMENT

FIG. 1 shows a sectional view of a head section 100 that is one exampleof the component placing head according to the first embodiment of thepresent invention.

As shown in FIG. 1, the head section 100 is provided with a suctionnozzle 2 that is one example of the component holding member forreleasably sucking and holding an electronic component 1 such as a chipcomponent as one example of the component. Although not shown, this headsection 100 is used while being equipped for an electronic componentplacing apparatus for placing the electronic component 1 on a circuitboard held on a machine base. The head section 100 is movably supportedroughly parallel to the surface of the circuit board by, for example, anX-Y robot above the machine base and is able to execute the componentplacing operation of making the suction nozzle 2 of the head section 100releasably hold the electronic component 1, thereafter aligning inposition the placement position of the electronic component 1 on thecircuit board with the held electronic component 1 and moving down thesuction nozzle 2 to place the electronic component 1 in the placementposition of the circuit board. It is to be noted that the positionalalignment is also executed in the head section 100 by rotatively movingthe suction nozzle 2 around an axis of rotation (axial center) thereofthat is the axial center thereof (i.e., rotation by an angle of θ) inaddition to the movement of the head section 100 itself by the X-Yrobot. That is, the suction nozzle 2 is able to elevatably move androtatively move in the head section 100.

The structure of the above-mentioned head section 100 will be describedin detail. As shown in FIG. 1, the head section 100 is provided with ashaft section 10 that is one example of a shaft section to be detachablyequipped for the suction nozzle 2, an elevation unit 20 for moving upand down the suction nozzle 2 equipped for the shaft section 10 via thisshaft section 10 and a rotating unit 30 for rotating the suction nozzle2 around the axis of rotation thereof (i.e., rotating it by an angle ofθ) via the shaft section 10.

Moreover, in the electronic component placing apparatus equipped withthe above-mentioned head section 100, there is often used a techniquefor increasing the amount of electronic components 1 that can be held ata time by a plurality of suction nozzles 2 equipped for the head sectionin order to improve the placement efficiency by reducing the timerequired for placing the electronic component 1 on the circuit board.The head section 100 of the present first embodiment is also able to beequipped with eight suction nozzles 2 as one example. That is, the headsection 100 is provided with eight sets of shaft sections 10 andelevation units 20. The shaft sections 10 are arranged at a constantinterval pitch in a line (i.e., the suction nozzles 2 equipped for theshaft sections 10 are arranged at the constant interval pitch in aline), and the elevation units 20 are arranged in a line so as tocorrespond one to one to the respective shaft sections 10. Moreover, theeight sets of shaft sections 10 and elevation mechanisms 20 aresupported by a head frame 40 provided for the head section 100 in theabove-mentioned arrangement. Moreover, the rotating unit 30 is able torotate the four suction nozzles 2 equipped for the mutually adjacentfour shaft sections 10. In the head section 100 capable of beingequipped with eight suction nozzles 2, two rotating units 30 areprovided while being supported by the head frame 40.

(Regarding the Shaft Section)

With regard to the head section 100 having the above-mentionedconstruction, the detailed structure of the shaft section 10 will bedescribed first. It is to be noted that the eight shaft sections 10provided for the head section 100 have similar structures. Therefore, inthe following description of the structure of the shaft section 10, oneshaft section 10 out of these shaft sections will be described unlessspecially mentioned.

As shown in FIG. 1, each of the shaft sections 10 is provided with aspline shaft 11, at the end portion of which (lower end in the figure) anozzle attaching portion 11 a that is one example of the holding memberattaching portion detachably equipped with the suction nozzle 2 isformed. Moreover, in order to make rotatable the suction nozzle 2equipped for the nozzle attaching portion 11 a via the spline shaft 11,the spline shaft 11 is made rotatable around the axis R of rotationthereof (being also the axial center of the spline shaft 11) by thecorresponding rotating unit 30. Moreover, in order to similarly make theequipped suction nozzle 2 elevatable via the spline shaft 11, the splineshaft 11 can be moved up and down along the axis R of rotation by thecorresponding elevation unit 20.

As described above, in a state in which this spline shaft 11 isrotatable and elevatable in the shaft section 10, the shaft section 10is supported by the head frame 40. Next, the support structure of thisshaft section 10 will be described with reference to the partiallyenlarged schematic view of the shaft section 10 shown in FIG. 2.

As shown in FIG. 2, the shaft section 10 is further provided with afirst spline nut 12 (arranged on the upper side in the figure) and asecond spline nut 13 (arranged on the lower side in the figure), whichhave a roughly cylindrical shape and are arranged apart from the splineshaft 11 along the axis R of rotation of the spline shaft 11 so that theinner peripheral surface thereof is brought in contact with the outerperipheral surface of the spline shaft 11, and which are two spline nutsfor elevatably supporting the spline shaft 11.

Moreover, as shown in FIG. 2, the shaft section 10 is further providedwith a first outer cylinder collar 14 that is one example of a firstcylindrical member, which has a roughly cylindrical shape and the innerperipheral surface of which has a first nut fixation portion 14 a thatis one example of a nut fixation portion fixed to the outer peripheralsurface (outer peripheral portion) of the first spline nut 12, and asimilar second outer cylinder collar 15 that is one example of a secondcylindrical member, which has a roughly cylindrical shape and the innerperipheral surface of which has a second nut fixation portion 15 a thatis one example of a nut fixation portion fixed to the outer peripheralsurface (outer peripheral portion) of the second spline nut 13.

Moreover, as shown in FIG. 2, a stepped portion 14 c is formed on thefirst outer cylinder collar 14 so that the diameter of the upper side ofthe first nut fixation portion 14 a is reduced at the upper end of thefirst nut fixation portion 14 a. Moreover, the outer peripheral surface(assumed to be the first support portion 14 b that is one example of thesupport portion) of the portion where the diameter of this steppedportion 14 c is formed small is rotatably supported via a bearingsection 51 on the inner peripheral surface of the shaft frame 41 (oneexample of the shaft support section) that has a roughly cylindricalshape provided for the head frame 40. Moreover, a stepped portion 15 cis formed at the second outer cylinder collar 15 so that the diameter onthe lower side in the figure of the second nut fixation portion 15 a isreduced at the lower end in the figure of the second nut fixationportion 15 a. Moreover, the outer peripheral surface (assumed to be asecond support portion 15 b that is one example of the support portion)of the portion where the diameter of this stepped portion 15 c is formedsmall is rotatably supported via a bearing section 52 on the innerperipheral surface of the shaft frame 41.

As described above, the first spline nut 12 and the second spline nut 13are arranged apart from each other. Therefore, as shown in FIG. 2, thefirst spline nut 12 and the bearing section 51 are arranged in thevicinity of the upper end in the figure of the shaft frame 41, while thesecond spline nut 13 and the bearing section 52 are arranged in thevicinity of the lower end in the figure of the shaft frame 41.

Moreover, as shown in FIG. 2, the first nut fixation portion 14 a andthe outer peripheral surface of the first spline nut 12 are fixed toeach other so that the lower portion on the outer peripheral surface ofthe first spline nut 12 is partially exposed from the first nut fixationportion 14 a of the first outer cylinder collar 14. Likewise, the secondnut fixation portion 15 a and the outer peripheral surface of the secondspline nut 13 are fixed to each other so that the upper portion on theouter peripheral surface of the second spline nut 13 is partiallyexposed from the second nut fixation portion 15 a of the second outercylinder collar 15. Further, the shaft section 10 is provided with anintermediate collar 16, which is one example of a cylindrical jointmember having a roughly cylindrical shape and has its roughlycylindrical inner peripheral surface bonded to the exposed outerperipheral surfaces of the first spline nut 12 and the second spline nut13.

It is to be noted that the diameter (outside diameter) of the outerperipheral surface of each of the first spline nut 12 and the secondspline nut 13, the diameter (inside diameter) of the inner peripheralsurface (inner peripheral portion) of the first nut fixation portion 14a of the first outer cylinder collar 14, the diameter (inside diameter)of the inner peripheral surface (inner peripheral portion) of the secondnut fixation portion 15 a of the second outer cylinder collar 15 and thediameter (inside diameter) of the inner peripheral surface of theintermediate collar 16 are formed so as to have approximately samedimension. Further, both end portions in the vertical direction of theintermediate collar 16, which is fixed to the outer peripheral surfacesof the first spline nut 12 and the second spline nut 13, are connectedto the end portions of the first outer cylinder collar 14 and the secondouter cylinder collar 15.

Moreover, in the first outer cylinder collar 14, the stepped portion 14c is formed so that the diameter of the outer peripheral surface of thefirst support portion 14 b is approximately equal to the diameter of theinner peripheral surface of the first nut fixation portion 14 a (i.e.,the diameter of the outer peripheral surface of the first spline nut 12)or preferably smaller than the diameter of the inner peripheral surface(e.g., smaller by a dimensional range of about 1 mm to the thicknessdimension of the first spline nut 12). Moreover, in the second outercylinder collar 15, the stepped portion 15 c is similarly formed so thatthe diameter of the outer peripheral surface of the second supportportion 15 b is approximately equal to the diameter of the innerperipheral surface of the second nut fixation portion 15 a (i.e., thediameter of the outer peripheral surface of the second spline nut 13) orpreferably smaller than the diameter of the inner peripheral surface(e.g., smaller by a dimensional range of about 1 mm to the thicknessdimension of the second spline nut 13). Moreover, a gap is providedbetween the inner peripheral surface of the shaft frame 41 and the outerperipheral surfaces of the first outer cylinder collar 14, the secondouter cylinder collar 15 and the intermediate collar 16, the gapassuring no contact between them.

In the head section 100 of the present first embodiment, the componentsare formed so that, for example, the outside diameter of the splineshaft 11 is 8 mm, the outside diameter of the (first and second) splinenuts 12 and 13 is 15 mm, the diameter of the outer peripheral surface ofthe (first and second) nut fixation portions 14 a and 15 a of the (firstand second) outer cylinder collars 14 and 15 is 18 mm, the diameter ofthe outer peripheral surface of the (first and second) support portions14 b and 15 b is 12 mm and the outside diameter of the bearing sections51 and 52 is 21 mm. Moreover, the first spline nut 12 and the secondspline nut 13 are arranged apart from each other at a distance of 50 mmbetween the center positions thereof and at a distance of 25 mm by thedimension between the end portions thereof in the direction along theaxis R of rotation.

Moreover, the first spline nut 12, the second spline nut 13, the firstouter cylinder collar 14, the second outer cylinder collar 15 and theintermediate collar 16 are bonded together in the above-mentionedrelations of arrangement and configuration. With this arrangement, thefirst spline nut 12 and the second spline nut 13 are put in anintegrated state while being joined together via the intermediate collar16. Also, the first spline nut 12 and the second spline nut 13, whichare put in the integrated state, are rotatably supported on the innerperipheral surface of shaft frame 41 via the bearing section 51 at thefirst support portion 14 b of the first outer cylinder collar 14 and viathe bearing section 52 at the second support portion 15 b of the secondouter cylinder collar 15, respectively. In the present first embodiment,the first outer cylinder collar 14, the second outer cylinder collar 15and the intermediate collar 16 serve as one example of the cylindricalmember that join the first spline nut 12 and the second spline nut 13together and put the same into the integrated state. The first splinenut 12 and the second spline nut 13 are arranged in the innercylindrical portion of the cylindrical member, and the outer peripheralsurfaces (portions) thereof are fixed to the inner peripheral surface(portion) of the cylindrical member.

Therefore, with the shaft section 10 having the above-mentionedstructure, the spline shaft 11 can move up and down along the axis R ofrotation inside the first spline nut 12 and the second spline nut 13 inthe shaft section 10, and the spline shaft 11 is rotatable around theaxis R of rotation together with the first spline nut 12 and the secondspline nut 13 and further with the first outer cylinder collar 14, thesecond outer cylinder collar 15 and the intermediate collar 16.

There is accepted the case where the first outer cylinder collar 14, thesecond outer cylinder collar 15 and the intermediate collar 16 areoriginally formed as an integrated body instead of the case where thefirst outer cylinder collar 14, the second outer cylinder collar 15 andthe intermediate collar 16 are formed as separate components andthereafter assembled together into the integrated body. The above isbecause the first spline nut 12 and the second spline nut 13 can bejoined together into an integrated body even in the above-mentionedcase.

(Regarding the Rotating Unit)

Next, the detailed structure of the rotating unit 30 will be describednext. As shown in FIG. 1, the rotating unit 30 is also provided with ashaft gear 31 that is one example of the transmission gear section,which has a roughly cylindrical configuration and is arranged so thatthe spline shaft 11 penetrates through the inside thereof, and on whichthe outer peripheral surface of which a plurality of teeth 31 a areformed. Moreover, the shaft gear 31 is arranged so that the axis ofrotation thereof roughly coincides with the axis R of rotation of thespline shaft 11 and able to rotate the spline shaft 11 around the axis Rof rotation by rotating the first spline nut 12 and the second splinenut 13 put in the integrated state by being rotated around the axis ofrotation thereof.

Further, the rotating unit 30 has a cogged belt 32 on which innerperipheral surface a plurality of teeth 32 a capable of being engagedwith the teeth 31 a of the shaft gear 31 and is further provided andwhich engaged with the shaft gear 31, a driving gear 33 on which aplurality of teeth 33 a capable of being engaged with the teeth 32 a ofthe cogged belt 32 are formed, and a rotating drive motor 34 that isprovided with the driving gear 33 fixed to the end of its driving shaft34 a (one example of the rotating drive shaft) and is able to rotate thedriving shaft 34 a in either the forward or reverse rotationaldirection. It is to be noted that the driving gear 33 and the rotatingdrive motor 34 serve as one example of the rotating drive section thatdrives the cogged belt 32 to make the same rotate (or run) in the firstembodiment.

Moreover, as shown in FIG. 2, the first support portion 14 b of thefirst outer cylinder collar 14 is extended upward in the figure with itsdiameter maintained, and the extended portion of the first outercylinder collar 14 is rotatably supported by the shaft frame 41 via thebearing section 53 by the outer peripheral surface of an upper supportportion 14 d that is the end portion of the extended portion. Moreover,a portion of the outer peripheral surface placed between the bearingsection 51 and the bearing section 53 at the extended portion of thefirst outer cylinder collar 14 is a gear fixation portion 14 e (also theextended portion of the first support portion 14 b), and the innerperipheral surface of the shaft gear 31 is bonded and fixed to this gearfixation portion 14 e. At the gear fixation portion 14 e, a spacecapable of juxtaposing two shaft gears 31 is secured along the axis R ofrotation of the spline shaft. However, in FIG. 2, the shaft gear 31 isfixed to the upper portion in the figure of the gear fixation portion 14e. Moreover, FIG. 2 shows the case where the shaft gear 31 is fixed tothe lower portion of the gear fixation portion 14 e by the imaginarylines in the figure. Moreover, a gap is provided between the innerperipheral surface of the gear fixation portion 14 e of the first outercylinder collar 14 and the outer peripheral surface of the spline shaft11, the gap assuring no contact between them. As described above, withthe shaft gear 31 fixed to the first outer cylinder collar 14 at thegear fixation portion 14 e, it is possible to rotate the first outercylinder collar 14 by rotating the shaft gear 31 and further rotate thespline shaft 11 around the axis R of rotation by rotating the firstspline nut 12 and the second spline nut 13 put in the integrated statearound the axis R of rotation.

In this case, the relation in plane among the shaft gears 31, the coggedbelts 32 and the driving gears 33 will be described here with referenceto the schematic explanatory view shown in FIG. 3.

As shown in FIG. 3, the head section 100 is provided with two rotatingunits 30. Eight shaft gears 31, which are arranged mutually adjacentlyat specified intervals in a line, are grouped into groups of four on theleft-hand side and four on the right-hand side in the figure, and thegroups of the shaft gears 31 belong to the respective rotating units 30.It is to be noted that the two rotating units 30 are grouped into therotating unit 30 located on the left-hand side in the figure and therotating unit 30 located on the left-hand side in the figure. However,since the rotating units have similar structures, only the rotating unit30 located on the left-hand side in the figure will be explained as arepresentative in the following description.

As shown in FIG. 3, in the rotating unit 30 located on the left-handside in the figure, the four shaft gears 31 are arranged at specifiedintervals in a line. The shaft gears 31 are assumed to be constituted ofa first shaft gear 31-1 (one example of the first transmission gearsection), a second shaft gear 31-2 (one example of the secondtransmission gear section), a third shaft gear 31-3 (one example of thethird transmission gear section) and a fourth shaft gear 31-4 (oneexample of the fourth transmission gear section) in order from theleft-hand side toward the right-hand side in the figure. Moreover, withregard to the first shaft gear 31-1 and the third shaft gear 31-3 of theshaft gears 31, the shaft gears 31 are fixed to the fixation position ofthe shaft gears 31 (i.e., the position located on the upper side in FIG.2) indicated by the solid line in the gear fixation portion 14 e of FIG.2. On the other hand, with respect to the second shaft gear 31-2 and thefourth shaft gear 31-4, the shaft gears 31 are fixed to the fixationposition of the shaft gears 31 (i.e., the position located on the lowerside in FIG. 2) indicated by the imaginary line in the gear fixationportion 14 e of FIG. 2.

Moreover, as shown in FIG. 3, the rotating unit 30 located on theleft-hand side in the figure is provided with two cogged belts 32 of afirst cogged belt 32-1 arranged on the left-hand side in the figure anda second cogged belt 32-2 arranged on the right-hand side in the figure.The first cogged belt 32-1 and the second cogged belt 32-2 are engagedwith one driving gear 33 by the inner peripheral surfaces thereof.Further, the first cogged belt 32-1 is engaged with the first shaft gear31-1 and the third shaft gear 31-3 by the inner peripheral surfacethereof, while the second cogged belt 32-2 is engaged with the secondshaft gear 31-2 and the fourth shaft gear 31-4 by the inner peripheralsurface thereof.

As shown in FIG. 1, the driving gear 33 has teeth 33 a, which are formedvertically in two rows so as to be engageable with the respective coggedbelts 32. An upper row side driving gear 33 b, which is located on theupper row side of the two rows, is engaged with the first cogged belt32-1, while a lower row side driving gear 33 c, which is located on thelower row side, is engaged with the second cogged belt 32-2. That is, asshown in FIG. 1, the first cogged belt 32-1 and the second cogged belt32-2 have a relation of mutually vertical arrangement. The first coggedbelt 32-1 is arranged on the upper side in the figure, and the secondcogged belt 32-2 is arranged on the lower side in the figure, so thatthe cogged belts 32 do not interfere with each other. It is to be notedthat the first shaft gear 31-1, the third shaft gear 31-3 and the upperrow side driving gear 33 b are arranged at same height of placement,while the second shaft gear 31-2, the fourth shaft gear 31-4 and thelower row side driving gear 33 c are arranged at same height ofplacement. Therefore, the first cogged belt 32-1 and the second coggedbelt 32-2, which have the aforementioned mutually vertical arrangement,are arranged roughly parallel to each other.

Moreover, as shown in FIG. 3, a tension roller 35-1 is provided betweenthe first shaft gear 31-1 and the driving gear 33 so as to consistentlyurge the first cogged belt 32-1 toward the inside thereof, consistentlyapplying a constant tension force to the first cogged belt 32-1 for theretention of a firm engagement relation among the first shaft gear 31-1,the third shaft gear 31-3, the upper row side driving gear 33 b and thefirst cogged belt 32-1. Likewise, a tension roller 35-2 is providedbetween the fourth shaft gear 31-4 and the driving gear 33 so as toconsistently urge the second cogged belt 32-2 toward the inside thereof,consistently applying a constant tension force to the second cogged belt32-2 for the retention of a firm engagement relation among the secondshaft gear 31-2, the fourth shaft gear 31-4, the lower row side drivinggear 33 c and the second cogged belt 32-2.

As shown in FIGS. 1, 2 and 3, a rotational driving force or the tensionforce is applied to the shaft gears 31 by the cogged belts 32. However,the first outer cylinder collar 14, which fixes the shaft gears 31 andis surely supported by the bearing sections 51 and 53 at both upper andlower ends of the gear fixation portion 14 e, therefore scarcelyreceives the influence of the rotational driving force or the tensionforce.

With the rotating unit 30 having the above-mentioned structure, byrotatively driving the rotating drive motor 34 in either the forward orreverse rotational direction, the driving gears 33 are rotatively drivenin the above-mentioned rotational direction via the driving shaft 34 a,and the first cogged belt 32-1 engaged with the upper row side drivinggear 33 b and the second cogged belt 32-2 engaged with the lower rowside driving gear 33 c are concurrently driven to run along theabove-mentioned rotational direction. By this operation, the first shaftgear 31-1 and the third shaft gear 31-3 engaged with the first coggedbelt 32-1 are concurrently driven to rotate in the above-mentionedrotational direction, while the second shaft gear 31-2 and the fourthshaft gear 31-4 engaged with the second cogged belt 32-2 areconcurrently driven to rotate in the above-mentioned rotationaldirection. As a result, in the shaft sections 10 (one example of thefirst shaft section through the fourth shaft section) corresponding tothe four shaft gears 31, the first spline nut 12 and the second splinenut 13 are rotatively driven around the respective axes R of rotationvia the respective first outer cylinder collars 14 fixed to therespective shaft gears 31, allowing the respective spline shafts 11 toconcurrently rotate around the axes R of rotation.

(Regarding the Elevation Unit)

The structure of the elevation unit 20 will be described in detail next.It is to be noted that the eight elevation units 20 provided for thehead section 100 have similar structures. Therefore, in the followingdescription of the elevation units 20, the structure of one elevationunit 20 out of these elevation units will be described unless speciallymentioned.

First of all, as shown in FIG. 1, the elevation unit 20 is provided witha ball screw shaft 21 that is one example of the ball screw shaftsection supported by the elevation frame 42 provided for the head frame40 rotatably around the axis S of rotation arranged roughly parallel tothe axis R of rotation of the spline shaft 11. The elevation unit 20 isfurther provided with an elevation drive motor 22 that is one example ofthe rotating drive section, which is fixed to the upper end portion inthe figure of the ball screw shaft 21 and rotates the ball screw shaft21 in either the forward or reverse rotational direction around the axisS of rotation, and an elevation nut section 23, which is meshed with theball screw shaft 21 and moved up and down along the axis S of rotationby the rotation of the ball screw shaft 21. Moreover, the elevation unit20 is further provided with an elevation bar 24 that is one example ofthe engagement member formed of a roughly L-figured rigid body, whichhas one end fixed to the elevation nut section 23 and is moved up anddown integrally with the ascent and descent of the elevation nut section23. Moreover, the elevation bar 24 is arranged so that the end portion24 a, which is the other end of this elevation bar 24, is engaged withthe upper portion of the spline shaft 11 via two bearing sections 25fixed apart from each other to the upper portion of the spline shaft 11.Moreover, the end portion 24 a of this elevation bar 24 has a roughlyU-figured shape. The end portion 24 a of the elevation bar 24 and theouter ring portion of the two bearing sections 25 are fixed to eachother so as to hold the two bearing sections 25 inside the roughlyU-figured shape, the engagement of the elevation bar 24 with the splineshaft 11 is achieved. Moreover, the two bearing sections 25 are fixed tothe upper portion of the spline shaft 11 by its inner ring portion, andtherefore, the engagement of the elevation bar 24 with the spline shaft11 does not hinder the rotation of the spline shaft 11 around the axis Rof rotation.

Moreover, as shown in FIG. 1, an annular spring receiving section 26 isfixed to the lower surface of the bearing section 25 located on thelower side in the figure among the two bearing sections 25 fixed to thespline shaft 11, and the upper end of a spring 27 arranged in an annularshape on the outer periphery of the spline shaft 11 is attached to thelower end of this spring receiving section 26. Further, as shown in FIG.1, an annular stepped portion 14 f is formed on the inner peripheralsurface of the gear fixation portion 14 e of the first outer cylindercollar 14 of the shaft section 10, and the lower end of the spring 27 isattached to this stepped portion 14 f.

This spring 27 plays a role of supporting the spline shaft 11 supportedby the first spline nut 12 and the second spline nut 13 elevatably alongthe axis R of rotation so that the spline shaft does not fall due to itsown weight or the like and consistently urging upward the spline shaft11 so as to put the engagement positions of the elevation bar 24 and thespline shaft 11 into a state in which they are more securely retained.

With the elevation unit 20 having the above-mentioned structure, theelevation nut section 23 meshed with the ball screw shaft 21 can bemoved up or down along the axis S of rotation by driving the elevationdrive motor 22 to rotate in either the forward or reverse the rotationaldirection to rotate the ball screw shaft 21 around the axis S ofrotation in the rotational direction. Further, the elevation bar 24fixed to this elevation nut section 23 is to be moved up or down alongthe axis S of rotation together with the elevation nut section 23. Dueto the engagement of this elevation bar 24 with the spline shaft 11, thespline shaft 11 can be moved up or down along the axis R of rotation insynchronization with the ascent or descent of the elevation nut section23. This spline shaft 11 is moved up or down along the inner peripheralsurfaces of the first spline nut 12 and the second spline nut 13. It isto be noted that the amount of ascent or descent of the elevation nutsection 23 can directly be the amount of ascent or descent of the splineshaft 11 by the state of secure engagement of the end portion 24 a ofthe elevating bar 24 with the spline shaft 11. That is, by controllingthe rotational drive amount of the elevation drive motor 22, the amountof elevation of the spline shaft 11 can be controlled. It is to be notedthat the end portion 24 a of the elevation bar 24, which is to move upand down the spline shaft 11 via the bearing section 25 located on thelower side, exerts no influence on the rotational operation of thespline shaft 11.

Moreover, when the ball screw shaft 21 is rotated around the axis S ofrotation thereof by the rotatively driven elevation drive motor 22 ineach elevation unit 20, the elevation nut section 23 receives a rotationmoment around the axis S of rotation, and the elevation bar 24 fixed tothis elevation nut section 23 also similarly receives a rotation moment.In the above-mentioned case, due to the fact that the end portion 24 aof the elevation bar 24 has the roughly U-figured shape, this rotationmoment is to be transmitted to the spline shaft 11 via each bearingsection 25. This spline shaft 11, which is formed so as to have rigidityresistible to this rotation moment, is able to restrict the rotationaround the axis S of rotation of the elevation bar 24 and the elevationnut section 23. Therefore, the elevation bar 24 and the elevation nutsection 23 have their movement in the rotational direction consistentlyrestricted only by the engagement of the elevation bar 24 with thespline shaft 11, and the elevation nut section 23 can be moved up anddown along the axis S of rotation by the rotation of the ball screwshaft 21.

(Assembling Procedure of the Shaft Section)

The procedure for assembling the components in the shaft section 10 ofthe head section 100 having the above-mentioned construction will bedescribed next.

First of all, in FIG. 2, the first nut fixation portion 14 a of thefirst outer cylinder collar 14 is fastened and fixed to the outerperipheral surface of the first spline nut 12 in the state in which thefirst spline nut 12 and the second spline nut 13 areassembled to thespline shaft 11, and the second nut fixation portion 15 a of the secondouter cylinder collar 15 is similarly fastened and fixed to the outerperipheral surface of the second spline nut 13. Further, the innerperipheral surface of the intermediate collar 16 is bonded and fixed toeach of the portion of the outer peripheral surface of the first splinenut 12 exposed from the first outer cylinder collar 14 and to the outerperipheral surface of the second spline nut 13 exposed from the secondouter cylinder collar 15, joining the first spline nut 12 to the secondspline nut 13.

As described above, the first support portion 14 b located in theposition where the first outer cylinder collar 14 is supported by thebearing section 51 and the second support portion 15 b located in theposition where the second outer cylinder collar 15 is supported by thebearing section 52 are concurrently processed in a state in which thespline shaft 11, the first spline nut 12, the second spline nut 13, thefirst outer cylinder collar 14, the second outer cylinder collar 15 andthe intermediate collar 16 are assembled together. The nozzle attachingportion 11 a, which is the portion to be detachably equipped with thesuction nozzle 2, of the spline shaft 11 is concurrently processed.Further, the upper support portion 14 d located in the position (alsothe upper end portion of the first outer cylinder collar 14) where thefirst outer cylinder collar 14 is supported by the bearing section 53 isalso concurrently processed. The processing of the above-mentionedportions is carried out in a state in which the spline shaft 11 isrotated around the axis R of rotation so that the axes of rotation ofthe above-mentioned portions coincide with the axis R of rotation of thespline shaft 11 by, for example, finely cutting the outer peripheralsurface and the end portions of the above-mentioned portions.

After effecting the processing as described above, the shaft gear 31 isinserted into and fixed to the gear fixation portion 14 e of the firstouter cylinder collar 14, and this assembly is inserted into the shaftframe 41 in a state in which the spline shaft 11, the first spline nut12, the second spline nut 13, the first outer cylinder collar 14, thesecond outer cylinder collar 15, the intermediate collar 16 and theshaft gear 31 are assembled together. The shaft section 10 is supportedby the shaft frame 41 via the bearing sections 51, 52 and 53. The shaftsection 10 can be thus assembled and supported by the shaft frame 41.Moreover, with regard to the production accuracy (i.e., allowance limitsof error of the design dimensions and work dimensions) of the componentsin the shaft section 10, the first outer cylinder collar 14, the secondouter cylinder collar 15 and the intermediate collar 16 are producedwithin an accuracy of about 20 μm. As a result of effecting theprocessing in the state in which the components produced with theabove-mentioned production accuracy are assembled together, amisalignment (i.e., concentricity) of the axis R of rotation of thespline shaft 11 with respect to the support sections of the bearingsections 51, 52 and 53 can be restrained to about 10 to 30 μm.

The shaft gear 31 is to be fixed to the gear fixation portion 14 e ofthe first outer cylinder collar 14 by its inner peripheral surface. Theconcentricity of the axis of rotation of the shaft gear 31 with respectto the axis R of rotation of the spline shaft 11 can be within adimensional error of about 20 μm in terms of the production accuracywith respect to the inner peripheral surface of the shaft gear 31 andthe gear fixation portion 14 e of the first outer cylinder collar 14.

(Regarding the Component Placing Operation by the Head Section)

Next, the operation of sucking and holding the electronic component 1 bythe head section 100, which having the aforementioned construction isattached to the X-Y robot of the aforementioned electronic componentplacing apparatus (not shown), and place the electronic component 1sucked and held to the mounting position of the component 1 on thecircuit board held on the machine base in the electronic componentplacing apparatus will be described next.

First of all, the head section 100 is moved along the surface of thecircuit board by the X-Y robot so that the suction nozzles 2 of the headsection 100 are located above an electronic component supply section inwhich a plurality of electronic components 1 are ejectably supplied inthe electronic component placing apparatus.

Subsequently, in each of the elevation units 20 of the head section 100of FIG. 1, the elevation drive motor 22 is rotatively driven in eitherthe forward or reverse rotational direction with its rotational driveamount controlled, moving down the elevation nut section 23 along theaxis S of rotation via the ball screw shaft 21. By this operation, theelevation bar 24 is moved down in each of the elevation units 20,depressing downward the bearing section 25 engaged with its end portion24 a. By this operation, the spring 27 is contracted, and the splineshaft 11 is moved down along the axis R of rotation while being slid onthe inner peripheral surface of the first spline nut 12 and the secondspline nut 13. In each of the shaft sections 10, the end portion of thesuction nozzle 2 comes in contact with the upper surface of theelectronic component 1, and the suction nozzle 2 sucks and holds theelectronic component 1. Subsequently, in each of the elevation units 20,the rotational direction of the elevation drive motor 22 is reversed,and the elevation bar 24 is moved up. In accordance with the ascent ofthis elevation bar 24, the spline shaft 11 is moved up along the axis Rof rotation, and the electronic component 1 sucked and held by thesuction nozzle 2 is moved up and taken out of the electronic componentsupply section. At this time, since the spline shaft 11 is consistentlyurged upward by the spring 27 in each of the elevation units 20, thespline shaft 11 is moved up while the position of elevation of thespline shaft 11 is restricted by the end portion 24 a of the elevationbar 24.

There may be either the case where the suction nozzles 2 areconcurrently moved up and down in the head section 100 to suck and holdand take out the electronic components 1 or the case where the suctionnozzles 2 are successively moved up and down to suck and hold and takeout the electronic components 1.

Subsequently, the head section 100 is moved by the X-Y robot upwardly ofthe circuit board in the electronic component placing apparatus. In thismovement process, by picking up the image of the electronic components 1sucked and held by the suction nozzles 2 of the head section 100 (bypicking up the image by, for example, a camera provided for the machinebase of the electronic component placing apparatus or a camera providedfor the head section 100 (neither one is shown) or the like), thesucked-and-held posture of the electronic component 1 by each of thesuction nozzles 2 is recognized. On the basis of the recognition resultof each sucked-and-held posture, the sucked-and-held posture iscorrected so that the sucked-and-held posture coincide with the placedposture (posture of placement in the placement position), and theelectronic components 1 are to be placed in the respective placementpositions on the circuit board.

For example, a displacement in the rotational direction around the axisR of rotation may occur between the sucked-and-held posture and theplacement posture of the electronic component 1. In such a case, thedisplacement can be corrected (hereinafter referred to as a θcorrection) by rotatively moving (i.e., rotating by an angle of θ) thesuction nozzle 2 around the axis R of rotation.

The procedure for executing the θ correction in the head section 100will be described in concrete. First of all, the θ correction isexecuted sequentially from the electronic component 1 sucked and held bythe suction nozzle 2 that firstly performs the placing operation of theelectronic component 1 among the eight suction nozzles 2 provided forthe head section 100. For example, when the shaft gear 31 attached tothe shaft section 10 equipped with this suction nozzle 2 is the shaftgear 31-1 shown in FIG. 3, the rotating drive motor 34 in the rotatingunit 30 located on the left-hand side in the figure is first rotativelydriven in either the forward or reverse rotational direction with itsrotational drive amount controlled on the basis of the rotational angleto be subjected to the θ correction, driving the first cogged belt 32-1to run along the rotational direction via the upper row side drivinggear 33 b. By this operation, the first shaft gear 31-1 is rotated bythe rotational angle in the rotational direction around the axis ofrotation thereof. At this time, due to the structure of the rotatingunit 30, the second shaft gear 31-2, the third shaft gear 31-3 and thefourth shaft gear 31-4 are concurrently rotated by the same rotationalangle in the same rotational direction.

In accordance with the above-mentioned rotation of the first shaft gear32-1, the first outer cylinder collar 14 integrally fixed to the gearfixation portion 14 eto the inner peripheral surface of the first shaftgear 32-1 is rotatively driven. Further, the first outer cylinder collar14, the second outer cylinder collar 15, the intermediate collar 16, thefirst spline nut 12 and the second spline nut 13, which are put in amutually integrated state, are rotatively driven around the axis R ofrotation, and the spline shaft 11 is also rotated around the axis R ofrotation by the aforementioned angle in the rotational direction. Bythis operation, the suction nozzle 2 equipped for the nozzle attachingportion 11 a of the spline shaft 11 is rotatively moved around the axisR of rotation by the aforementioned rotational angle, effecting the θcorrection of the electronic component 1.

At this time, as described above, the nozzle attaching portion 11 a, thefirst support portion 14 b, the second support portion 14 c and theupper support portion 14 d are concurrently processed in the state inwhich the spline shaft 11, the first spline nut 12, the second splinenut 13, the first outer cylinder collar 14, the second outer cylindercollar 15 and the intermediate collar 16 are assembled together.Therefore, the concentricity of the axes of rotation is improved, andthe θ correction can be executed with high accuracy.

In the rotating unit 30, the suction nozzle 2 by which the placingoperation of the electronic component 1 is executed next, i.e., oneshaft gear 31 is selected from among the second shaft gear 31-2, thethird shaft gear 31-3 and the fourth shaft gear 31-4, and the θcorrection is executed according to a similar procedure.

Moreover, as shown in FIG. 3, the head section 100 is provided with thetwo rotating units 30 that have the same structure. Therefore, the θcorrection can be concurrently executed also in the rotating unit 30located on the right-hand side in the figure while executing the 0correction in the rotating units 30 located on the left-hand side in thefigure. By thus concurrently executing the θ correction in the headsection 100, the time for executing the θ correction for all the suctionnozzles 2 can be reduced.

Subsequently, the positional alignment of the suction nozzle 2 by whichthe placing operation is performed first among the suction nozzles 2provided for the head section 100 with the placement position of thecircuit board is carried out by the X-Y robot. After the positionalalignment, the elevation drive motor 22 is driven to rotate in eitherthe forward or reverse rotational direction with its rotational driveamount controlled in the elevation unit 20 corresponding to the suctionnozzle 2, moving down the elevation nut section 23 along the axis S ofrotation via the ball screw shaft 21. By this operation, the elevationbar 24 is moved down to depress downward the bearing sections 25 engagedwith the end portion 24 a thereof. By this operation, the spring 27 iscontracted, and the spline shaft 11 is moved down along the axis R ofrotation while being slid on the inner peripheral surfaces of the firstspline nut 12 and the second spline nut 13. Subsequently, the lowersurface of the electronic component 1 held by the suction nozzle 2 comesin contact with the placement position of the circuit board. In theplacement position of the circuit board, a bonding material of solder orthe like is preparatorily supplied, and the lower surface of theelectronic component 1 is further pressed against the bonding material.In this state, the descent by the elevation unit 20 is stopped, and thesucking and holding of the electronic component 1 by the suction nozzle2 is released. Subsequently, the spline shaft 11 is moved up by theelevation unit 20 to move up the suction nozzle 2, and the electroniccomponent 1 is placed in the placement position of the circuit board.Subsequently, operation similar to the above will be repetitivelyexecuted for the other suction nozzles 2 to place the respectiveelectronic components 1 on the circuit board.

The operation of placing a plurality of electronic components 1 on thecircuit board can be thus executed by the head section 100.

In this case, FIG. 7 shows a schematic sectional view of part of a headsection 200 according to a modification example of the head section ofthe present first embodiment, and the structure of a portion to bejoined to the elevation unit and the spline shaft will be described indetail with reference to FIG. 7. It is to be noted that the basicstructure of the head section 200 described below is roughly similar tothat of the head section 100 shown in FIG. 1, and the detailedstructural section is more concretely shown. Moreover, similarly to thehead section 100, the head section 200 is provided with eight splineshafts (or suction nozzles) and eight elevation units correspondingindependently to the spline shafts. However, since they have a mutuallyidentical structure, the relation between one set of spline shafts andthe elevation units thereof will be explained in the followingdescription.

As shown in FIG. 7, the elevation unit 220 provided for the head section200 is provided with a ball screw shaft 221 that is one example of theball screw shaft section rotatably supported by an elevation frame 242around the axis S of rotation (the H shaft) arranged in the samedirection (i.e., the perpendicular direction) as that of the axis R ofrotation of the spline shaft 211. In concrete, the ball screw shaft 221provided with the axial center thereof as the axis S of rotation has itsboth end portions fixed to the elevation frame 242 (by using, forexample, a fixing nut section 261 or the like) via bearing sections(only the bearing section 262 for fixing the end portion on the upperside is shown in the figure). Moreover, the end portion on the upperside of the ball screw shaft section 221 is joined to an elevation drivemotor 222 via a coupling 260. By being rotatively driven around the axisS of rotation as a consequence of the transmission of the rotating driveby this elevation drive motor 222 to the ball screw shaft 221 via thecoupling 260, an elevation nut section 223 meshed with the ball screwshaft 221 can be moved up and down. Moreover, the elevation unit 220 isprovided with an elevation bar 224, which has one end fixed to theelevation nut section 223 and is one example of the engagement memberformed of a rigid body having a roughly L-figured shape moved up anddown integrally with the ascent and descent of the elevation nut section223. Moreover, this elevation bar 224 is formed by fastening a jointbracket-B 224 b that is the one end fixed to the elevation nut section223 to a joint bracket-A 224 a engaged with the spline shaft 211 bymeans of, for example, screwing.

Moreover, as shown in FIG. 7, the spline shaft 211, of which the axialcenter is arranged so as to roughly coincide with its axis R ofrotation, is rotatably supported by a head frame (not shown) via (firstand second) spline nuts. The upper end side of the spline shaft 211 isthe portion to be engaged with the joint bracket-A 224 a, and theengagement between the joint bracket-A 224 a and the spline shaft 211 isachieved via a bearing section-A 225A and a bearing section-B 225Battached to the outer periphery of the spline shaft 211.

More in detail, the end portion of the joint bracket-A 224 a has aroughly ring-like shape. By fixing the roughly ring-shaped inside of thejoint bracket-A 224 a to the outer ring portions of the bearingsection-A 225A and the bearing section-B 225B so that the bracket holdboth the bearing section-A 225A and the bearing section-B 225B insidethe roughly ring-like shape, the aforementioned engagement is achieved.Moreover, the inner ring portions of the bearing section-A 225A and thebearing section-B 225B are fixed to the outer peripheral surface of thespline shaft 211, and a spacer 263 that is arranged so as to bury theinner ring portions of the bearing sections is further fixed to theouter peripheral surface of the spline shaft 211. It is to be noted thata gap is provided between the joint bracket-A 224 a and the spacer 263,the gap assuring no contact between them.

Moreover, an annular spring receiving section 226 is fixed to the lowerportion of the inner ring of the bearing section-B 225B, and the upperend of the spring 227 is attached to the lower end of this springreceiving section 226. It is to be noted that the lower end of thespring 227 is attached to an annular stepped portion formed on the innerperipheral surface of the gear fixation portion of the first outercylinder collar of a shaft section (not shown). With the above-mentionedspring 227 or the like provided, the spline shaft 211 whose own weightis supported by the elevation unit 220 via the elevation bar 224 issupported by the spring 227 instead of the support by the elevation unit220 when, for example, electrification to the elevation drive motor 222of the elevation unit 220 is interrupted (e.g., during power failure orthe like), allowing this spline shaft 211 to be prevented from falling.The reason why the joint bracket-A 224 a and the joint bracket-B 224 bare fastened to each other by screwing in the elevation bar 224 is forfine adjustment of the positions of the axes R and S of rotation in thehead section 200.

Moreover, an upper shaft 265 is arranged above the spline shaft 211 onthe axis R of rotation, and a lower portion of this upper shaft 265 isintegrally fixed to the upper end of the spline shaft 211 by fasteningby screwing or the like. Moreover, a metal bearing section 264 forguiding the ascent and descent of the upper shaft 265, which is moved upand down integrally with the spline shaft 211, is formed on theleft-hand side in the figure in the upper portion of the elevation frame242. Moreover, an air joint 266, which is the joined portion to bejoined to a vacuum unit, is provided at the upper end of the upper shaft265. The upper shaft 265 and the spline shaft 211 have hollow holes,which are both formed along the respective axial centers and mutuallycommunicating, allowing vacuum to reach the end of the suction nozzlefrom the vacuum unit via the air joint 266 and the hollow holes andallowing the end portion of the suction nozzle to suck and hold anelectronic component.

According to the construction and function of the above-mentioned headsection 200, the elevation nut section 223 can be moved up and down inthe elevation unit 220 by rotatively driving the elevation drive motor222 and rotating the ball screw shaft 221 around the axis S of rotationvia the coupling 260. With the ascent of this elevation nut section 223,the elevation bar 224 fixed to the elevation nut section 223 is alsomoved up and down integrally with the elevation nut section 223, and theelevating operation of the spline shaft 211 along the axis R of rotationcan be performed via the bearing section-A 225A and the bearingsection-B 225B.

In this elevating operation, the elevation nut section 223 is to receivea reactive force generated when the ball screw shaft 221 is rotated bythe elevation drive motor 222. In the conventional construction of theelevation unit that employs a ball screw shaft and an elevation nutsection, there is the general practice of restricting (guiding) thepivot by the reactive force of the elevation nut section by using an LMguide (e.g., LM guide 526 of FIG. 4) or the like in order to resist sucha reactive force. In contrast to this, the embodiment of the presentmodified example adopts a structure that employs the two bearingsections of the bearing section-A 225A and the bearing section-B 225B inthe upper portion of the spline shaft 211, providing a constructionresisting the reactive force by the spline shaft 211 itself. With thisarrangement, the LM guide, which has been employed in the conventionalconstruction, is made unnecessary. This allows the gap between thespline shaft 211 and the ball screw shaft 221 (i.e., the gap between theaxis R of rotation and the axis S of rotation) can be shortened,allowing the downsizing of the head section 200 to be achieved.

Moreover, in the construction of the above-mentioned present embodiment,the spline shaft 211 is required to have a mechanical rigiditysufficient for resisting the reactive force. The required mechanicalrigidity is sometimes higher than the mechanical rigidity required formounting an electronic component with high accuracy. Therefore, thepresent embodiment contributes to the substantial improvement of therigidity of the spline shaft 211 by providing the metal bearing section264 for elevatably supporting (guiding) the upper shaft 265 integratedwith the spline shaft 211 without increasing the diameter of the splineshaft 211. There can be considered a technique for providing one moreset of spline nuts for elevatably rotatably supporting the spline shaft211 instead of the above-mentioned technique for improving the rigidity.However, this technique has a problem that the spline shaft 211 issometimes unable to move up and down or rotate when its axial center isslightly displaced with respect to the axis R of rotation due to thereactive force received by the spline shaft 211, errors in producing andassembling the spline shaft and the like, and therefore, it cannot besaid that this technique is a preferable technique. In the presentembodiment, for example, a gap of about 30 to 50 μm is provided betweenthe metal bearing section 264 and the peripheral surface of the uppershaft 265 in order to prevent in advance the occurrence of theabove-mentioned problem in the metal bearing section 264.

(Effects of the First Embodiment)

According to the aforementioned first embodiment, the following variouseffects can be obtained.

First of all, the first outer cylinder collar 14 and the second outercylinder collar 15 are fixed by the first nut fixation portion 14 a andthe second nut fixation portion 15 a, respectively, to the outerperipheral surface of the first spline nut 12 and the second spline nut13 that are arranged apart each other in each of the shaft sections 10of the head section 100 and are able to elevatably support the splineshaft 11 along the axis R of rotation, and the inner peripheral surfaceof the intermediate collar 16 is bonded and fixed. With thisarrangement, the two spline nuts of the first spline nut 12 and thesecond spline nut 13 can be joined to each other and put in anintegrated body.

Further, the two spline nuts put in the integrated body can be rotatablysupported around the axis R of rotation by the shaft frame 41 via thetwo bearing sections 51 and 52 in the first support portion 14 b of thefirst outer cylinder collar 14 and the second support portion 15 b ofthe second outer cylinder collar 15. That is, the two spline nuts can berotatably supported by the two bearing sections 51 and 52, and theamount of bearing sections to be placed for supporting the spline nutsin each of the shaft sections 10 can be reduced.

For example, although each of the shaft section 510 is provided with twospline nuts similarly to the head section 100 of the first embodiment inthe conventional head section 500, the four bearing sections areattached to support the two spline nuts. However, in the head section100 of the first embodiment, the amount of bearing sections to be placedcan be reduced, and this allows the assembling of the shaft sections 10in the head section 100 to be facilitated and allows the production costof the head section 100 to be reduced. Moreover, since the amount ofbearing sections to be placed is also reduced, the positional alignmentof the axes R of rotation of the spline shafts 11 with the axis ofrotation of the bearing sections (also the axes of rotation of the firstouter cylinder collar 14 and the second outer cylinder collar 15 in thefirst embodiment) can be facilitated (i.e., the places to be subjectedto the positional alignment can be reduced). Therefore, the quantity ofdisplacement due to the rotation of the suction nozzle 2 in the shaftsection 10 can be reduced, and the rotational accuracy can be improved.

Moreover, instead of supporting the spline nuts directly by the outerperipheral surfaces thereof by the shaft frame 41 via the bearingsections, the stepped portion 14 c is formed between the first supportportion 14 b and the first nut fixation portion 14 a so that the outsidediameter of the portion 14 b becomes approximately equal to orpreferably smaller than the inside diameter of the portion 14 a in thefirst outer cylinder collar 14, and the stepped portion 15 c is formedbetween the second support portion 15 b and the second nut fixationportion 15 a so that the outside diameter of the portion 15 b similarlybecomes approximately equal to or preferably smaller than the insidediameter of the portion 15 a in the second outer cylinder collar 15. Bysupporting the two spline nuts via the first support portion 14 b, thesecond support portion 15 b and the two bearing sections 51 and 52, theinside diameter of the bearing sections can be made approximately equalto or smaller than the outside diameter of the spline nuts whilereducing the amount of the bearing sections to be placed.

As described above, when the inside diameter of the bearing section canbe reduced, the outside diameter of each shaft section 10 can bereduced, and the arrangement interval between the spline shafts 11provided for the head section 100 can be narrowed, allowing a downsizedhead section 100 to be provided.

Conversely, when the outside diameter of the shaft section 10 is notreduced, the outside diameter of the spline shaft 11 can be increasedwithout changing the outside diameter of the shaft section 10, and therigidity of the spline shaft 11 can be improved. In such a case, thegeneration of the displacement or the like of the axis R of rotation ofthe spline shaft 11 can be restrained by the rigidity even when, forexample, an external force is applied to the spline shaft 11 during thereplacement of the suction nozzle 2 or another case, and a head sectionhaving a higher rotational accuracy can be provided.

Moreover, by cutting the outer peripheral surfaces of the first supportportion 14 b in the position where the first outer cylinder collar 14 issupported by the bearing 51, the second support portion 15 b in theposition where the second outer cylinder collar 15 is supported by thebearing 52 and the upper support portion 14 d in the position where thefirst outer cylinder collar 14 is supported by the bearing section 53while rotating the spline shaft 11 around the axis R of rotation in thestate in which the spline shaft 11, the first spline nut 12, the secondspline nut 13, the first outer cylinder collar 14, the second outercylinder collar 15 and the intermediate collar 16 are integrallyassembled in attaching each of the shaft section 10 to the head section100, the axis of rotation of the portions that have undergone themachining can be made to roughly coincide with the axis of rotation ofthe spline shaft 11 with high accuracy. Furthermore, the shaft section10 can be rotatably supported by the shaft frame 41 via the bearingsections 51, 52 and 53 by inserting the shaft section 10 assembled inthe above-mentioned state into the shaft frame 41, and a head section100 having a high rotational accuracy can be provided.

As a concrete example, although the components of the shaft section 510are produced with a production accuracy of about 10 μm in theconventional head section 500, the displacement of the axes of rotationfurther occurs during assembly, and a concentricity of about 50 μm to 70μm is achieved after the assembling. On the other hand, in the headsection 100 of the first embodiment, the cutting is carried out afterthe components are assembled even if the first outer cylinder collar 14,the second outer cylinder collar 15 and the intermediate collar 16 areproduced with a production accuracy of about 20 μm. Therefore, aconcentricity of about 10 to 30 μm can be finally obtained.

Moreover, dissimilarly to the conventional case where the shaft gear isattached to the outer cylinder collar 516 via the coupling 535 in eachof the shaft sections 10, the shaft gear 31 is directly fixed to thegear fixation portion 14 e of the first outer cylinder collar 14 in thestate in which the concentricity is improved as described above.Therefore, the concentricity of the axis of rotation of the shaft gear31 with respect to the axis R of rotation of the spline shaft 11 can beimproved.

Moreover, dissimilarly to the conventional case where the four shaftgears 531 are engaged with one another inside the one cogged belt 532 ineach of the rotating units, the first cogged belt 32-1 and the secondcogged belt 32-2 are provided as the two cogged belts in each of therotating units 30, the first cogged belt 32-1 is engaged with the firstshaft gear 31-1 and the third shaft gear 31-3, and the second coggedbelt 32-2 is engaged with the second shaft gear 31-2 and the fourthshaft gear 31-4. Therefore, the areas of engagement of the four shaftgears 31 can be uniformed in the state in which the areas of engagementof the cogged belts with the shaft gears 31 are sufficiently secured.With this arrangement, the deviation in the rotational accuracy, whichhas been generated by the deviation in the area of engagement, can becanceled. Further, by sufficiently securing the areas of engagement,each of the shaft gears 31 can reliably be driven to rotate, and thesuction nozzles 2 can be rotated with high rotational accuracy.

As a concrete example, in contrast to the fact that the rotationalaccuracy of the θ-rotation by the rotating unit 530 is about 0.2 degreesin the conventional head section 500, the rotational accuracy of theθ-rotation by the rotating unit 30 can be improved to 0.01 degrees orless in the head section 100 of the first embodiment.

In each of the elevation units 20, the movement of the elevation bar 24and the elevation nut section 23 in the rotational direction thereof isconsistently restricted by only the engagement between the elevation bar24 and the spline shaft 11, and the elevation nut section 23 can bemoved up and down along the axis S of rotation by the rotation of theball screw shaft 21. However, the above-mentioned structure can beprovided by forming large the outside diameter of the spline shaft 11 bythe support structure with the outside diameters of the bearing sections51 and 52 maintained in the shaft section 10 for the improvement of therigidity (i.e., strength) as described by the aforementioned effects.Therefore, in the support structure in which the outside diameter of thespline shaft 511 cannot be formed large (i.e., for the reason that theentire head section becomes disadvantageously large if the externalshape is formed large) as in the conventional head section 500, the LMguide 526, which has been needed to receive the rotation momenttransmitted from the elevation nut section 523 to the spline shaft 511via the elevation bar 524, can be made unnecessary in the head section100 of the first embodiment. With this arrangement, the dimensionbetween the axis R of rotation of the spline shaft 11 and the axis S ofrotation of the ball screw shaft 21 can be reduced by obviating the needfor the LM guide, and a head section, 100 further reduced in size can beprovided. For example, the aforementioned dimension can be reduced byabout 30 to 40 mm in comparison with that of the conventional headsection.

SECOND EMBODIMENT

The present invention is not limited to the aforementioned embodimentbut able to be provided in a variety of embodiments. For example, FIG. 8shows a schematic sectional view of a head section 300 that is oneexample of the component placing head according to the second embodimentof the present invention.

As shown in FIG. 8, the head section 300 basically has a structuresimilar to that of the head section 100 of the first embodiment shown inFIG. 1. Therefore, the components having structures similar to thosedescribed above are denoted by the same reference numerals as in FIG. 1,and no description is provided therefor. Moreover, in the description ofthe construction and functions of the following head section 300, theconstruction and functions of the elevation unit 20 that hascharacteristic construction and actions in the present second embodimentwill be described more in detail than in the first embodiment.

As shown in FIG. 8, in the elevation unit 20 of the head section 300,the axis S of rotation of the axial center of the ball screw shaft 21 isassumed as an elevating operation axis, and the elevation nut section 23is moved up and down along the elevating operation axis, and theelevating operation range is restricted between an upper end positionand a lower end position. In concrete, the elevation nut section 23 canbe moved up and down along the axis S of rotation between an upper endside restriction frame 43 that is one example of the restricting portionfixed and attached to the elevation frame 42 in an upper portion of theball screw shaft 21 (below the elevation drive motor 22) and a lower endside restriction frame 44 that is one example of the restricting portionfixed and attached to the elevation frame 42 in a lower portion of theball screw shaft 21. Moreover, by bringing the upper end of theelevation nut section 23 being moved upward in contact with the lowerend of the upper end side restriction frame 43, the upward movement ofthe elevation nut section 23 is restricted in this position of contact.Moreover, by bringing the lower end of the elevation nut section 23being moved downward in contact with the upper end of the lower end siderestriction frame 44, the downward movement of the elevation nut section23 in this position of contact is restricted.

Moreover, each of the elevation units 20 provided for the head section300 is provided with an encoder 71 that is one example of the rotationalangle detecting section capable of detecting the rotational angle aroundthe axis S of rotation of the elevation drive motor 22. In each of theelevation units 20, the encoder 71 can detect a relative rotationalangle with respect to the origin of rotation by setting one point of therotational angle as the origin of rotation. Moreover, the variation ofthis rotational angle has a relation proportional to the amount ofrotation of the ball screw shaft 21 and the amount of elevatingoperation of the elevation nut section 23.

Further, each of the elevation units 20 is provided with an overloaddetecting section 72 capable of detecting the overload of the elevationdrive motor 22. In each of the elevation units 20, the overloaddetecting section 72 can detect the overload of the elevation drivemotor 22 when, for example, the upper end of the elevation nut section23 comes in contact with the upper end side restriction frame 43 andthis position of elevation is limited while the elevation drive motor 22attempts to perform the rotational driving.

(Regarding the Light Transmission Unit)

In the head section 300 that has the above-mentioned construction, theelevation units 20 move up and down the suction nozzles 2 along the axesR of rotation via the respective spline shafts 11 in the shaft sections10, thereby carrying out the sucking and taking-out operation and theplacing operation of electronic components 1. During these operations,it is important which height position the suction nozzle 2 is moved upfrom and which height position the suction nozzle 2 is moved down toalong the axis R of rotation thereof. Therefore, each of the elevationunits 20 that carry out the elevating operation can execute origindetecting operation (this origin detecting operation will be describedlater) for detecting the origin position that becomes a reference heightposition of the elevating operation. By executing the above-mentionedorigin detecting operation periodically or arbitrarily in the headsection 300, the reliable elevating operation of each of the suctionnozzles 2 in the head section 300 is guaranteed.

The head section 300 is provided with a light transmission unit 60 thatexecutes part of the above-mentioned origin detecting operation, and thestructure of this light transmission unit 60 will be described.

As shown in FIG. 8, the light transmission unit 60 is provided with alight-projecting section 61 and a light-receiving section 62, which arearranged opposite to each other, in a direction along the arraydirection of the ball screw shafts 21, and the light-projecting section61 and the light-receiving section 62 are attached and fixed to theelevation frame 42 so that the ball screw shafts 21 thereof are arrangedbetween the light-projecting section 61 and the light-receiving section62. FIGS. 9A through 9D are explanatory views schematically showing theorigin detecting operation (method) in the head section 300. As shown inFIG. 9A, the light-projecting section 61 and the light-receiving section62 are provided on the elevation frame 42 (not shown in FIGS. 9A through9D) with the relations of arrangement thereof maintained. Moreover, thelight-projecting section 61 can irradiate light from a light-emittingsection 61 a provided on the light-receiving section 62 side of thelight-projecting section 61 toward the light-receiving section 62, whilethe light-receiving section 62 can receive and detect the light emittedfrom the light-projecting section 61 in a light-detecting section 62 aprovided on the light-projecting section 61 side of the light-receivingsection 62. Moreover, as shown in FIGS. 9A through 9D, an optical axis Tis arranged between the light-emitting section 61 a and thelight-detecting section 62 a so that the light, which is emitted fromthe light-emitting section 61 a and received and detected by thelight-detecting section 62 a, is roughly parallel to the array directionof the ball screw shafts 21 and roughly perpendicular to the axis S ofrotation of each of the ball screw shafts 21.

FIGS. 10A through 10C show schematic explanatory views of the elevationunit 20, viewed in the direction of arrow A in FIGS. 9A through 9D. Asshown in FIG. 10A, the optical axis T located between thelight-detecting section 62 a and the light-emitting section 61 a (notshown in FIGS. 10A through 10C) in the light transmission unit 60 isarranged on the left-hand side in the figure without interfering withthe ball screw shafts 21. Moreover, as shown in FIG. 10B or 10C, whenthe elevation nut section 23 is moved down along the ball screw shaft21, the left-hand portion in the figure of the elevation nut section 23can interfere with the optical axis T.

With the optical axis T thus arranged, when at least one elevation nutsection 23 among the elevation nut sections 23 provided for the headsection 300 is located in a position where the nut section interfereswith the optical axis T by the elevating operation thereof (e.g., in thestate of FIG. 10B or 10C), the light emitted from the light-projectingsection 61 is interrupted by at least one elevation nut section 23 andnot received by the light-receiving section 62. Conversely, when all theelevation nut sections 23 in the head section 300 are located inpositions where the nut sections do not interfere with the optical axisT by the elevating operation thereof (e.g., in the state of FIG. 10A),the light emitted from the light-projecting section 61 is received bythe light-receiving section 62 while being interrupted by none of theelevation nut sections 23.

In this case, the height position along the elevating operation axis(also the axis S of rotation) of the elevation nut section 23 in each ofthe elevation units 20 of the head section 300 will be described withreference to the schematic explanatory view shown in FIG. 11. It is tobe noted that each of the height positions shown in FIG. 11 is theposition at the lower end of the elevation nut section 23. Since theelevation units 20 provided for the head section 300 perform similarelevating operation, one elevation unit 20 out of the elevation units 20will be described with reference to FIG. 11.

As shown in FIG. 11, the elevation nut section 23 can move up and downbetween an upper end position of the elevating operation at a height ofH=+2 mm and a lower end position of the elevating operation at a heightof H=−65 mm with respect to the axial origin (H=0 mm) that is the originof elevation served as a reference height position. Moreover, theoptical axis T of the light transmission unit 60 is located at a heightof H=−7 mm. The optical axis T is arranged so that the optical axis Tdoes not interfere with the elevation nut section 23 in the state inwhich the lower end position of the elevation nut section 23 is locatedat the height of H=−6 mm, and the optical axis T interferes with theelevation nut section 23 in the state in which the lower end position ofthe elevation nut section 23 is located at the height of H=−8 mm.

In the present specification, a “prescribed light interruptiondimension” is assumed to mean a dimension (i.e., 7 mm) from the axialorigin (H=0 mm) to the height position (H=−7 mm) where the optical axisT is arranged. However, taking the arrangement error of the heightposition of the optical axis T, the production error of the elevationnut section 23 and so on into consideration, it is preferable to set theprescribed light interruption dimension slightly greater than theaforementioned dimension to set the height position where theinterruption of light is reliably detected. In the present embodiment,the dimension is set within the height position of H=−8 mm (i.e., 8 mm).

Moreover, the height position relation of the elevation nut section 23is synchronized with the height position relation of the spline shaft 11and the suction nozzle 2 corresponding to this elevation nut section 23.For example, the height position of H=−63 mm is the nozzle replacementheight of the suction nozzle 2 equipped for the nozzle attaching portion11 a of the spline shaft 11. By the elevating operation of the elevationnut section 23 mainly within a height position range of H=0 mm to H=−63mm, the placing operation of the electronic component 1 is executed bythe corresponding suction nozzle 2.

In each of the elevation units 20, the variation in the rotational angleof the elevation drive motor 22 detected by the encoder 71 and theamount of the elevating operation of the elevation nut section 23 are ina proportional relation, and the origin of rotation of the rotationalangle can be detected at a 12 mm pitch with respect to the position ofH=0 mm served as the reference position. That is, the origin of rotationcan be detected by the encoder 71 at each of the height positions ofH=0, 12, 24, 36, 48 and 60 mm.

(Regarding the Control Section)

Next, the control section for controlling the operations in the headsection 300 will be described next. As shown in FIG. 8, the head section300 is provided with a control section 9 that controls the sucking andholding operation of the electronic component 1 by each of the suctionnozzles 2, the elevating operation in each of the elevation units 20 andthe rotational operation in each of the rotating units 30. This controlsection 9 controls each of the suction nozzles 2, each of the elevationunits 20 and each of the rotating units 30 so that the operationsthereof are related to one another, thereby enabling the placingoperation of the electronic component 1 in the head section 300.

Moreover, the control section 9 is provided with an origin detectioncontrol section 8 that can control the origin detecting operation(method) for detecting the origin position of elevation of the elevationnut section 23 of each of the elevation units 20 in the head section300. The detailed origin detecting operation in the origin detectioncontrol section 8 will be described later. Moreover, as shown in FIG. 8,this origin detection control section 8 can receive inputs of thedetection's result (i.e., a rotational angle detection signal and anoverload detection signal) from the encoder 71 and the overloaddetecting section 72 provided for each of the elevation units 20.Moreover, emission of light and the presence or absence of interruptionof light of the emitted light in the light transmission unit 60 areinputted as detection signals to the origin detection control section 8,and the origin detection control section 8 can determine the presence orabsence of the interruption of light.

(Regarding the Origin Detecting Operation)

A method for detecting the origin of the elevating operation of theelevation nut section 23 in each of the elevation units 20 in the headsection 300 that has the aforementioned construction and function willbe described next. FIGS. 12 and 13 show a flowchart representing thisorigin detecting operation, and description is made on the basis of thisflowchart. Each action of this origin detecting operation is controlledby the origin detection control section 8 of the control section 9.

First of all, as shown in FIG. 9A, in each of the elevation units 20,the elevation drive motor 22 is driven to rotate, moving up theelevation nut section 23 located in an arbitrary height position on theelevating operation axis on the elevating operation axis (step S1 in theflowchart of FIG. 12). The elevated elevation nut section 23 has itsupper end brought in contact with the upper end side restriction frames43, and this event of contact is determined by detecting the overload ofthe elevation drive motor 22 by the overload detecting section 72 andinputting this detection result to the origin detection control section8 (step S2). It is to be noted that the ascent of the elevation nutsection 23 is effected until this overload detection is performed.Moreover, the height position where this overload detection is performedis a position of H=+2 mm in FIG. 4, and this state is the state shown inFIG. 9B. FIG. 9B shows the state in which the contact is made only inthe elevation nut section only 23 located at the left-hand end in thefigure.

When this overload is detected, then the rotational direction of theelevation drive motor 22 is reversed (step S3). By this operation, theelevation nut section 23 is moved down along the elevating operationaxis (step S4). During this descent, the origin of rotation of theelevation drive motor 22 is detected by the encoder 71, and the descentis effected until the origin of rotation is detected. When the origin ofrotation is detected by the encoder 71 (step S5), the rotational drivingof the elevation drive motor 22 is stopped, and the descent of theelevation nut section 23 is stopped. Further, the stop position of theelevation nut section (position at the lower end) on this elevatingoperation axis is set as an origin of elevation (i.e., set as an originpresumed to be the axial origin (this is hereinafter assumed to be thedetection origin)) in the origin detection control section 8, andsetting is performed assuming that the elevation nut section 23 islocated at the height position of H=0 mm in FIG. 11 (step S6).

The actions from the step S1 to the step S6 may be either in the casewhere the actions are executed concurrently in the elevation units 20 ofthe rotating unit 30 or in the case where the actions are executedsequentially. Subsequently, the detection origin is set in everyelevation nut section 23 provided for the head section 300, and theorigin detection control section 8 confirms the state of stop of theelevation nut sections 23 at the set detection origins (step S7). Whenthere is an elevation nut section 23 that is not stopped at thedetection origin with regard to the elevation nut sections 23, theactions from the step S1 to the step S6 are executed for the elevationnut section 23 (step S8). Moreover, the state in which all the elevationnut sections 23 provided for the head section 300 are stopped at therespective detection origins is shown in FIGS. 9C and 10A.

After confirming that all the elevation nut sections 23 are stopped atthe respective detection origins in the origin detection control section8, one elevation nut section 23 is selected from among all the elevationnut sections 23 (step S9 in the flowchart of FIG. 13), and the selectedelevation nut section 23 starts to move down from the detection origin(step S10). This descent is effected by detecting the rotational angleof the elevation drive motor 22 by the encoder 71 in a state in whichthe descent height position on the elevating operation axis isrecognized by the origin detection control section 8.

Subsequently, when the origin detection control section 8 determinesthat the lower end of the selected elevation nut section 23 is moveddown to the position of H=−6 mm in FIG. 11, the origin detection controlsection 8 detects the presence or absence of the interruption of lightemitted from the light-projecting section 61 toward the light-receivingsection 62 of the light transmission unit 60 (step S11). When theinterruption of light is not confirmed in step S11, the selectedelevation nut section 23 is not stopped, and the descent is continuouslyeffected. Subsequently, when it is determined that the lower end of theselected elevation nut section 23 is moved down to the position of H=−8mm in FIG. 11, i.e., moved down by the light interruption prescribeddimension in the origin detection control section 8, the origindetection control section 8 detects the presence or absence of theinterruption of light emitted from the light-projecting section 61toward the light-receiving section 62 of the light transmission unit 60(step S12). When the interruption of light is confirmed in step S12, theorigin detection control section 8 determines that the detection origincoincides with the axial origin with regard to the selected elevationnut section 23 (step S13). The irradiation of light by the lighttransmission unit 60 is only required to be effected at least inaccordance with the timing of the step S11 and the step S12, and thismay be performed either in the case where the irradiation of light iscontinuously effected in advance or in the case where the irradiation oflight is intermittently effected in accordance with the above-mentionedtiming. Moreover, the state of the elevation nut section 23 in step S12is the state shown in FIGS. 9D and 10B. FIG. 9D shows a state in whichthe elevation nut section 23 located secondly from the left-hand side inthe figure of each of the elevation nut sections 23 provided for thehead section 300 is moving down.

Moreover, when the interruption of light is detected by the origindetection control section 8 in step S11, the lower end of the selectedelevation nut section 23, which is estimated to be moved down to theposition of H=−6 mm, is interfering with the optical axis T of the lighttransmission unit 60 located at the position of H=−7 mm shown in FIG.11. This is interpreted as the incorrect detection of the detectionorigin and as the occurrence of a detection origin setting error (stepS16).

Likewise, when the interruption of light is not detected by the origindetection control section 8 in step S12, the lower end of the selectedelevation nut section 23, which is estimated to be moved down to theposition of H=−8 mm, is not interfering with the optical axis T of thelight transmission unit 60 located in the position of H=−7 mm shown inFIG. 11. This is interpreted as the incorrect detection of the detectionorigin and as the occurrence of a detection origin setting error (stepS16).

The selected elevation nut section 23, which has undergone confirmationof the detection origin in step S13 is moved up to the detection originposition (step S15), and the next one elevation nut section 23, whichhas not yet been selected, is selected from among the elevation nutsections 23 provided for the head section 300 (step S17). Subsequently,the procedure from the step S10 to the step S14 is similarly executedfor this selected next one elevation nut section 23. In step S15, whenthe origin detection control section 8 determines that the coincidenceof the detection origins of all the elevation nut sections 23 providedfor the head section 300 with the axial origins has been confirmed, thisorigin detecting operation is completed.

In the above description, the origin detecting operation is executed forall the elevation nut sections 23 provided for the head section 300.However, the origin detecting operation is not limited only to theabove-mentioned case, and there may be the case where the origindetecting operation is executed for only one elevation nut section 23.In such a case, if it is confirmed in step S15 that the confirmation ofthe axial origin has been executed for the elevation nut section 23 tobe subjected to the origin detection, then the origin detectingoperation ends.

Moreover, in the flowchart of the origin detecting operation shown inFIGS. 12 and 13, a series of operation from the step S1 to the step S8is one example of the origin setting means (or origin setting process),and a series of operation from the step S9 to the step S17 is oneexample of the origin confirming means (or origin confirming process).

Although the aforementioned origin detecting operation has been executedby concurrently using the encoder 71 and the overload detecting section72 provided for each of the elevation units 20 for the setting of thedetection origins according to the above description, the secondembodiment is not limited to this case. For example, in place of theabove-mentioned case, the overload detecting section 72 may not beprovided since the setting of the origin detection can be performed whenthe position of elevation on the elevating operation axis of theelevation nut section 23 can be detected only by the detection of therotational angle of the elevation drive motor 22 by the encoder 71.

Moreover, in the present second embodiment, the origin detectingoperation is executed by detecting that the light emitted from the lighttransmission unit 60 is interrupted directly by each of the elevationnut sections 23. Each of the elevation nut sections 23 is formed with aproduction dimension accuracy of, for example, about ±0.05 mm, by whichthe origin detection accuracy of the origin detecting operation can bewithin a range of about ±0.2 mm, and this allows reliable accurateorigin detection to be achieved.

(Suction Nozzle Interference Prevention Interlock)

Interference prevention interlock of the suction nozzle 2 utilizing thelight transmission unit 60 provided for the aforementioned head section300 will be described next.

As shown in FIGS. 8 and 11, each of the elevation nut sections 23provided for the head section 300 has its elevating operation upper endposition mechanically restricted by the upper end side restriction frame43 and has its lower end position mechanically restricted by the lowerend side restriction frame 44. As shown in FIG. 11, with regard to eachof the elevation nut sections 23, its height position along theelevating operation axis (i.e., the axis S of rotation) is elevatablewithin a range in which H=+2 mm to −65 mm. Moreover, the optical axis Tof the light transmission unit 60 has its height position set at H=−7mm, and the interruption of light is detected when arbitrary portions ofthe elevation nut section 23, including its lower portion, is located atthe height position of H=−7 mm.

When the elevation height position of each of the elevation nut sections23 is located on the lower side of the position of H=−7 mm, theinterruption of light can surely be detected by the light transmissionunit 60 by using the function of the aforementioned light transmissionunit 60. In concrete, each of the elevation nut sections 23 is formed sothat the upper portion of each of the elevation nut sections 23interferes with the optical axis T located in the position of H=−7 mm ina state in which each of the elevation nut sections 23 is located in theelevating operation lower end position (H=−65 mm). With thisarrangement, when each of the elevation nut section 23 is consistentlyinterfering with the optical axis T of the light transmission unit 60when located below the position of H=−7 mm, and the interference oflight is to be detected.

By thus forming each of the elevation nut sections 23, when oneelevation nut section 23 among the elevation nut sections 23 providedfor the head section 300 is located below the position of H=−7 mm, i.e.,when the suction nozzle 2 corresponding to the elevation nut section 23is located in the height position below the position of H=−7 mm, theinterference of light is surely detected by the light transmission unit60. By inputting this detection result to the control section 9 via theorigin detection control section 8, the control section 9 inhibits themovement of the main body of the head section 300 along the surface ofthe circuit board (i.e., the movement carried out by the X-Y robotprovided for the electronic component placing apparatus), enabling theprevention of the interference of the suction nozzle 2 located in theaforementioned lower height position with the constituent members of theelectronic component placing apparatus, the electronic components 1 andthe like mounted on the circuit board. That is, the detection of lightby the light transmission unit 60 can be the interference preventioninterlock of the suction nozzles 2 in the head section 300.

(Effects of the Second Embodiment)

According to the second embodiment, the following various effects can beobtained.

First of all, instead of performing the mounting operation of theelectronic components 1 by executing the elevating-operation of each ofthe suction nozzles 2 in the head section 300 using this detectionorigin as it is after the detection origin of elevation of each of theelevation nut sections 23 is set by detecting the origin of rotation ofeach of the elevation drive motors 22 by means of each of the encoders71 provided for the head section 300, it is confirmed whether or notthese set detection origins actually coincide with the axial origins.Therefore, even if a malfunction (setting error) occurs during thesetting of each of the detection origins, the setting error can reliablybe detected, and the possible occurrence of a placement error due to thefact that the detection origin does not coincide with the axial origincan be prevented in advance in the subsequent placing operation of theelectronic components 1, and reliable origin detection can be achieved.This allows the electronic component placing operation to be achievedwith high accuracy in the component placing apparatus provided with theaforementioned head section 300.

Moreover, the aforementioned origin detection can be achieved byproviding the head section 300 with only one light transmission unit 60,which is provided with the light-projecting section 61 and thelight-receiving section 62 arranged opposite to each other along thearray direction of the ball screw shafts 21, allowing the elevation nutsections 23 to be arranged between the light-projecting section 61 andthe light-receiving section 62, and detecting the presence or absence ofthe interruption of the light by the elevation nut section 23 byreceiving the light emitted from the light-projecting section 61 towardthe light-receiving section 62 by the light-receiving section 62.

That is, by the operation that the interruption of light is notdetected, by the light transmission unit 60, in which the heightposition of the optical axis T of the emission of light thereof is setto H=−7 mm, when one elevation nut section 23 is selected from among theelevation nut sections 23 in the state in which they are located in therespective set detection origin positions, the selected elevation nutsection 23 is moved down with respect to the set detection origin as areference, and the lower end of the selected elevation nut section 23 ismoved down to the height position of H=−6 mm. And the operation that theinterruption of light is detected by the light transmission unit 60 whenthe lower end is moved down to the height position of H=−8 mm, theorigin detection control section 8 determines that the set detectionorigin coincides with the axial origin of this elevation nut section 23,allowing the origin detection to be achieved. Moreover, for the otherelevation nut sections 23, the origin detection can be achieved byconfirming that the set detection origins coincide with the respectiveaxial origins according to a similar procedure through successiveselection.

Therefore, even when a plurality of, for example, eight suction nozzles2 are provided as in the head section 300, the confirmation of theorigin can be achieved by providing one light transmission unit 60 forthe head section 300 without providing each of the elevation units 20with a unit for the origin confirmation. Therefore, the head sectioncapable of executing reliable origin detection can be provided with asimple construction, and the production cost thereof can be suppressedlow.

Moreover, the light transmission unit 60 can detect whether or not thelight emitted from the light-projecting section 61 is directlyinterrupted by the elevation nut section 23. The construction of thehead section can be made simple without providing a special light shieldplate (e.g., DOG etc.) for the interruption of the light, and this cancontribute to the downsizing of the head section.

Moreover, by providing each of the elevation units 20 of the headsection 300 with the overload detecting section 72 in addition to theencoder 71, it is determined that the elevation nut section 23 has beenmoved up and the elevation nut section 23 has come in contact with theupper end side restriction frame 43 by the detection of the overload ofthe elevation drive motor 22 by the overload detecting section 72 duringthe setting of the detection origin of each of the elevation nutsections 23. When this detection is performed, the elevation drive motor22 is reversed to move down the elevation nut section 23, and after theinitiation of this descent, the lowered position of the elevation nutsection 23 when the origin of rotation of the elevation drive motor 22detected first by the encoder 71 is detected can be set as the detectionorigin position. With this arrangement, the setting of the detectionorigin can be achieved with the simple construction of the encoder 71and the overload detecting section 72 providing neither complicatedmechanism nor unit for this detection origin setting for the headsection 300.

Moreover, in the case where each of the elevation nut sections 23provided for the head section 300 has its elevation height positionlocated on the lower side of the position of H=−7 mm, when one elevationnut section 23 among the elevation nut sections 23 is located in theposition of H=−7 mm, i.e., when the suction nozzle 2 corresponding tothe elevation nut section 23 is located in the height position lowerthan the position of H=−7 mm with the formation such that theinterruption of light is surely detected by the light transmission unit60, the interruption of light can surely be detected by the lighttransmission unit 60. By inputting this detection result to the controlsection 9 via the origin detection control section 8, the controlsection 9 inhibits the movement of the main body of the head section 300along the surface of the circuit board (i.e., the movement carried outby the X-Y robot provided for the electronic component placingapparatus), enabling the prevention of the interference of the suctionnozzle 2 located in the aforementioned lower height position with theconstituent members of the electronic component placing apparatus, theelectronic components 1 and the like mounted on the circuit board. Thatis, the detection of light by the light transmission unit 60 can furtherbe the interference prevention interlock of the suction nozzle 2 in thehead section 300, and this can obviate the need for providing a specialsensor or the like for the provision of the interlock like this in thehead section 300, allowing the construction of the head section to besimple.

It is to be noted that, by appropriately combining arbitrary embodimentsof the aforementioned embodiments, the effects possessed by them can beproduced.

Although the present invention has been fully described in connectionwith the preferred embodiments thereof with reference to theaccompanying drawings, it is to be noted that various changes andmodifications are apparent to those skilled in the art. Such changes andmodifications are to be understood as included within the scope of thepresent invention as defined by the appended claims unless they departtherefrom.

1. A component placing head comprising: a plurality of component holdingmembers for releasably holding a plurality of component; a plurality ofshaft sections detachably equipped with each of the component holdingmembers; elevation units for executing elevating operations of thecomponent holding members; a rotating unit for executing rotationaloperation of each of the component holding members for correction ofholding postures of components held by the component holding members;and a head frame that has shaft support sections for supporting theshaft sections and supports the elevation units and the rotating unit,the component placing head being able to place the plurality ofcomponents held by the component holding members on a circuit board, theshaft sections each comprising: a spline shaft that has a holding memberattaching portion for detachably equipping with the component holdingmember at its end portion and is rotatable around an axis (R) ofrotation by the rotating unit, elevatable along the axis of rotation bythe elevation unit and arranged so as to penetrate the shaft supportsection; a first spline nut and a second spline nut that are arrangedapart from each other along the axis of rotation in vicinity of an upperend and a lower end, respectively, of the shaft support section andelevatably support the spline shaft; and cylindrical members that haveinner peripheral portions fixed to outer peripheral portions of thefirst spline nut and the second spline nut and join the first spline nutto the second spline nut so as to put the spline nuts into an integratedstate, and the cylindrical members being supported in the vicinity ofthe upper end and the lower end of the shaft support section rotatablyaround the axis of rotation via two bearing sections elevatably androtatably supporting the shaft section by the shaft support section. 2.The component placing head as defined in claim 1, wherein in each of theshaft sections, the spline shaft and the cylindrical members areprocessed cutting so that the axis of rotation of the spline shaftcoincides with the axes of rotation of the cylindrical members in astate in which the first spline nut, the second spline nut and thecylindrical members are assembled with the spline shaft.
 3. Thecomponent placing head as defined in claim 1, wherein the cylindricalmembers in each of the shaft sections are integrally formed of: thefirst cylindrical member that has a nut fixation portion whose innerperipheral portion is fixed to the outer peripheral portion of the firstspline nut and a support portion whose outer peripheral portion issupported by one bearing section of the two bearing sections; the secondcylindrical member that has a nut fixation portion whose innerperipheral portion is fixed to the outer peripheral portion of thesecond spline nut and a support portion whose outer peripheral portionis supported by the other bearing section of the two bearing sections;and the cylindrical joint member that join the first cylindrical memberto the second cylindrical member, and a stepped portion is formedbetween the support portion and the nut fixation portion so that adiameter of the outer peripheral portion of the support portion issmaller than a diameter of the inner peripheral portion of the nutfixation portion at each of the first cylindrical member and the secondcylindrical member.
 4. The component placing head as defined in claim 3,wherein the rotating unit comprises: a transmission gear section whoseinner peripheral portion is fixed to the outer peripheral portion of thesupport portion of either one of the first cylindrical member and thesecond cylindrical member in each of the shaft sections; a cogged beltthat internally has a plurality of teeth capable of being engaged withthe transmission gear section and is engaged with the transmission gearsection; and a rotating drive section that rotatively drives the coggedbelt, whereby the support portion is rotatively driven by rotativelydriving the transmission gear section around its axis of rotation viathe cogged belt by the rotating drive section in each of the shaftsections, enabling the spline shaft to be rotatably driven via the firstspline nut and the second spline nut.
 5. The component placing head asdefined in claim 4, further comprising: four shaft sections constructedof a first shaft section through a fourth shaft section arrangedmutually adjacent in a line as the shaft sections, wherein the rotatingunit comprising: four transmission gear sections constructed of a firsttransmission gear section through a fourth transmission gear sectionattached to the first shaft section to the fourth shaft section,respectively, as the transmission gear sections; and a first cogged beltengaged with only the first transmission gear section and the thirdtransmission gear section among the four transmission gear sections anda second cogged belt engaged with only the second transmission gearsection and the fourth transmission gear section as the cogged belts,and the rotating drive section comprising one rotating drive shaftsection that is engaged with the first cogged belt and the second coggedbelt and is able to rotatively drive both the first cogged belt and thesecond cogged belt.
 6. The component placing head as defined in claim 3,wherein each of the elevation units comprises: a ball screw shaftsection supported rotatably around its axis of rotation (S); a rotatingdrive section that is fixed to an end portion of the ball screw shaftsection and for rotating the ball screw shaft section around the axis ofrotation; an elevation nut section that is meshed with the ball screwshaft section and is elevatable along the axis of rotation center of theball screw shaft section by the rotation of the ball screw shaftsection; and an engagement member that is fixed to the elevation nutsection and engaged with the spline shaft of the corresponding shaftsection and is able to move up and down the spline shaft insynchronization with the ascent and descent of the elevation nutsection, and the elevation nut section is elevatable along the axis ofrotation in a state in which the rotation of the ball screw shaftsection around the axis of rotation is restricted only by the engagementof the engagement member with the spline shaft.
 7. The component placinghead as defined in claim 1, wherein the shaft sections are arrangedmutually in a line, the elevation units are comprised of a plurality ofelevation units that correspond one to one to the shaft sections and formoving up and down the shaft sections along the respective axes ofrotation, each of the elevation units comprises: a ball screw shaftsection supported rotatably around its axis of rotation; a rotatingdrive section that is fixed to an end portion of the ball screw shaftsection and for rotating the ball screw shaft section around the axis ofrotation; an elevation nut section that is meshed with the ball screwshaft section and is elevatable along the axis of rotation of the ballscrew shaft section by the rotation of the ball screw shaft section; andan engagement member that is fixed to the elevation nut section andengaged with the corresponding shaft section and able to move up anddown the shaft section in synchronization with the ascent and descent ofthe elevation nut section, the component placing head furthercomprising: light transmission unit that is provided with alight-projecting section and a light-receiving section arranged so as tobe opposite to each other in a direction along an array direction of theball screw shaft sections and able to arrange the elevation nut sectionsbetween the light-projecting section and the light-receiving section andable to detect presence or absence of interruption of light by theelevation nut section by receiving the light emitted from thelight-projecting section toward the light-receiving section by thelight-receiving section; a plurality of rotational angle detectingsections capable of detecting a rotational angle of the rotating drivesection provided for each of the elevation units; and an origindetection control section is operable to set an origin of elevation ofthe elevation nut section by detecting the rotational angle by therotational angle detecting section in each of the elevation units,individually move down the elevation nut sections located in respectiveset origin positions so that the light emitted from the light-projectingsection is received by the light-receiving section without beinginterrupted, detect the interruption of light emitted from thelight-projecting section by the lowered elevation nut section by thelight-receiving section in a position where the elevation nut section islowered from each of the set origins by a prescribed light interruptiondimension, thereby confirming the fact that the set origins are originsof elevation to execute the detection of the origins.
 8. The componentplacing head as defined in claim 7, wherein each of the elevation unitsfurther comprising: an overload detecting section capable of detectingoverload of the rotating drive section; and restricting portions thatare fixed to the ball screw shaft section while being located apart fromeach other and for restricting mechanically the upper end position andthe lower end position of elevation of the elevation nut section, andthe origin detection control section is operable to reverse therotational direction of the rotating drive section when the overload ofeach of the rotating drive sections is detected by the respectiveoverload detection section by moving each of the elevation nut sectionsto the upper end position of the elevating operation and bringing eachof the elevation nut sections in contact with the restricting portion inthe upper end position, and detect the rotational angle by therotational angle detection section in each of the elevation units afterthe reversing, whereby set the position along the axial center of theelevation nut section when the origin of rotation of the rotating drivesection is detected at a first time as the origin of elevation.
 9. Thecomponent placing head as defined in claim 7, wherein thelight-projecting section and the light-receiving section are arranged sothat the light emitted from the light-projecting section can betransmitted and received by the light-receiving section in each ofpositions located apart by the prescribed light interruption dimensiondownwardly along the axis of rotation of each of the ball screw shaftsections from each of the origins.
 10. The component placing head asdefined in claim 7, wherein each of the elevation nut sections canconsistently interrupt the light emitted from the light-projectingsection in the position of elevation of the elevation nut sectionbetween each of positions located apart by the prescribed lightinterruption dimension downwardly along each of the axes of rotationfrom each of the origins and a lower end position of elevation of theelevation nut section.
 11. An origin detection method for a componentplacing head (300) having: a plurality of shaft sections that has an endportion provided with a plurality of component holding members forreleasably holding components and are arranged in a line; a plurality ofelevation units that correspond one to one to the shaft sections and formoving up and down each of the shaft sections along its axis ofrotation, the elevation units being comprised of, a ball screw shaftsection supported rotatably around its axis of rotation, a rotatingdrive section that is fixed to an end portion of the ball screw shaftsection and for rotating the ball screw shaft section around the axis ofrotation, an elevation nut section that is meshed with the ball screwshaft section and is elevatable along the axis of rotation of the ballscrew shaft section by the rotation of the ball screw shaft section, andan engagement member that is fixed to the elevation nut section andengaged with the corresponding shaft section and able to move up anddown the shaft section in synchronization with the ascent and descent ofthe elevation nut section; and a light-projecting section and alight-receiving section, which are arranged opposite to each other in adirection along an array direction of the ball screw shaft sections andare able to arrange each of the elevation nut sections between thelight-projecting section and the light-receiving section and are able todetect the presence or absence of the interruption of light by theelevation nut section by receiving the light emitted from thelight-projecting section toward the light-receiving section by thelight-receiving section, whereby the components held by the componentholding members are placed on the circuit board, the method comprising:setting an origin of elevation of the elevation nut section by detectingthe rotational angle of the rotating drive section in each of theelevation units; individually moving down the elevation nut sectionslocated in the respective set origin positions so that the light emittedfrom the light-projecting section is received by the light-receivingsection without being interrupted; and confirming the fact that each ofthe set origins are origins of elevation by detecting the interruptionof light emitted from the light-projecting section by the loweredelevation nut section by the light-receiving section in a position wherethe elevation nut section is lowered from each of the set origins by aprescribed light interruption dimension to execute the detection of theorigins.
 12. The origin detection method for the component placing headdefined in claim 11, wherein, moving each of the elevation nut sectionsto an upper end position of its elevating operation, reversing therotational direction of the rotating drive section when overload of eachof the rotating drive sections is detected at each of the upper endpositions, and detecting the rotational angle of each of the elevationunits after the reversing, the position along the axis of rotation ofthe elevation nut section when the origin of rotation of the rotatingdrive section is detected at a first time can be set as the origin ofelevation.
 13. The origin detection method for the component placinghead defined in claim 11, wherein the light-projecting section and thelight-receiving section are arranged so that the light emitted from thelight-projecting section can be transmitted and received by thelight-receiving section in each of positions located apart by theprescribed light interruption dimension downwardly along the axis ofrotation of each of the ball screw shaft sections from each of theorigins.
 14. The origin detection method for the component placing headdefined in claim 11, wherein each of the elevation nut sections canconsistently interrupt the light emitted from the light-projectingsection in the position of elevation of the elevation nut sectionbetween each of positions located apart by the prescribed lightinterruption dimension downwardly along the axis of rotation from eachof the origins and a lower end position of elevation of the elevationnut section, and movement of each of the component holding members in adirection along a surface of the circuit board is inhibited in the statein which light is interrupted.